Depend on jekyll gem instead of github-pages

I don't think we need everything that github-pages pulls in, and this
should speed up the build.

Gemfile

@@ -1,3 +1,3 @@
 source 'https://rubygems.org'
 
-gem 'github-pages'
+gem 'jekyll'

Gemfile.lock

@@ -1,89 +1,16 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    activesupport (4.2.10)
-      i18n (~> 0.7)
-      minitest (~> 5.1)
-      thread_safe (~> 0.3, >= 0.3.4)
-      tzinfo (~> 1.1)
     addressable (2.5.2)
       public_suffix (>= 2.0.2, < 4.0)
-    coffee-script (2.4.1)
-      coffee-script-source
-      execjs
-    coffee-script-source (1.11.1)
     colorator (1.1.0)
-    commonmarker (0.17.13)
-      ruby-enum (~> 0.5)
     concurrent-ruby (1.1.1)
-    dnsruby (1.61.2)
-      addressable (~> 2.5)
     em-websocket (0.5.1)
       eventmachine (>= 0.12.9)
       http_parser.rb (~> 0.6.0)
-    ethon (0.11.0)
-      ffi (>= 1.3.0)
     eventmachine (1.2.7)
-    execjs (2.7.0)
-    faraday (0.15.3)
-      multipart-post (>= 1.2, < 3)
     ffi (1.9.25)
     forwardable-extended (2.6.0)
-    gemoji (3.0.0)
-    github-pages (192)
-      activesupport (= 4.2.10)
-      github-pages-health-check (= 1.8.1)
-      jekyll (= 3.7.4)
-      jekyll-avatar (= 0.6.0)
-      jekyll-coffeescript (= 1.1.1)
-      jekyll-commonmark-ghpages (= 0.1.5)
-      jekyll-default-layout (= 0.1.4)
-      jekyll-feed (= 0.10.0)
-      jekyll-gist (= 1.5.0)
-      jekyll-github-metadata (= 2.9.4)
-      jekyll-mentions (= 1.4.1)
-      jekyll-optional-front-matter (= 0.3.0)
-      jekyll-paginate (= 1.1.0)
-      jekyll-readme-index (= 0.2.0)
-      jekyll-redirect-from (= 0.14.0)
-      jekyll-relative-links (= 0.5.3)
-      jekyll-remote-theme (= 0.3.1)
-      jekyll-sass-converter (= 1.5.2)
-      jekyll-seo-tag (= 2.5.0)
-      jekyll-sitemap (= 1.2.0)
-      jekyll-swiss (= 0.4.0)
-      jekyll-theme-architect (= 0.1.1)
-      jekyll-theme-cayman (= 0.1.1)
-      jekyll-theme-dinky (= 0.1.1)
-      jekyll-theme-hacker (= 0.1.1)
-      jekyll-theme-leap-day (= 0.1.1)
-      jekyll-theme-merlot (= 0.1.1)
-      jekyll-theme-midnight (= 0.1.1)
-      jekyll-theme-minimal (= 0.1.1)
-      jekyll-theme-modernist (= 0.1.1)
-      jekyll-theme-primer (= 0.5.3)
-      jekyll-theme-slate (= 0.1.1)
-      jekyll-theme-tactile (= 0.1.1)
-      jekyll-theme-time-machine (= 0.1.1)
-      jekyll-titles-from-headings (= 0.5.1)
-      jemoji (= 0.10.1)
-      kramdown (= 1.17.0)
-      liquid (= 4.0.0)
-      listen (= 3.1.5)
-      mercenary (~> 0.3)
-      minima (= 2.5.0)
-      nokogiri (>= 1.8.2, < 2.0)
-      rouge (= 2.2.1)
-      terminal-table (~> 1.4)
-    github-pages-health-check (1.8.1)
-      addressable (~> 2.3)
-      dnsruby (~> 1.60)
-      octokit (~> 4.0)
-      public_suffix (~> 2.0)
-      typhoeus (~> 1.3)
-    html-pipeline (2.8.4)
-      activesupport (>= 2)
-      nokogiri (>= 1.4)
     http_parser.rb (0.6.0)
     i18n (0.9.5)
       concurrent-ruby (~> 1.0)
@@ -100,97 +27,10 @@ GEM
       pathutil (~> 0.9)
       rouge (>= 1.7, < 4)
       safe_yaml (~> 1.0)
-    jekyll-avatar (0.6.0)
-      jekyll (~> 3.0)
-    jekyll-coffeescript (1.1.1)
-      coffee-script (~> 2.2)
-      coffee-script-source (~> 1.11.1)
-    jekyll-commonmark (1.2.0)
-      commonmarker (~> 0.14)
-      jekyll (>= 3.0, < 4.0)
-    jekyll-commonmark-ghpages (0.1.5)
-      commonmarker (~> 0.17.6)
-      jekyll-commonmark (~> 1)
-      rouge (~> 2)
-    jekyll-default-layout (0.1.4)
-      jekyll (~> 3.0)
-    jekyll-feed (0.10.0)
-      jekyll (~> 3.3)
-    jekyll-gist (1.5.0)
-      octokit (~> 4.2)
-    jekyll-github-metadata (2.9.4)
-      jekyll (~> 3.1)
-      octokit (~> 4.0, != 4.4.0)
-    jekyll-mentions (1.4.1)
-      html-pipeline (~> 2.3)
-      jekyll (~> 3.0)
-    jekyll-optional-front-matter (0.3.0)
-      jekyll (~> 3.0)
-    jekyll-paginate (1.1.0)
-    jekyll-readme-index (0.2.0)
-      jekyll (~> 3.0)
-    jekyll-redirect-from (0.14.0)
-      jekyll (~> 3.3)
-    jekyll-relative-links (0.5.3)
-      jekyll (~> 3.3)
-    jekyll-remote-theme (0.3.1)
-      jekyll (~> 3.5)
-      rubyzip (>= 1.2.1, < 3.0)
     jekyll-sass-converter (1.5.2)
       sass (~> 3.4)
-    jekyll-seo-tag (2.5.0)
-      jekyll (~> 3.3)
-    jekyll-sitemap (1.2.0)
-      jekyll (~> 3.3)
-    jekyll-swiss (0.4.0)
-    jekyll-theme-architect (0.1.1)
-      jekyll (~> 3.5)
-      jekyll-seo-tag (~> 2.0)
-    jekyll-theme-cayman (0.1.1)
-      jekyll (~> 3.5)
-      jekyll-seo-tag (~> 2.0)
-    jekyll-theme-dinky (0.1.1)
-      jekyll (~> 3.5)
-      jekyll-seo-tag (~> 2.0)
-    jekyll-theme-hacker (0.1.1)
-      jekyll (~> 3.5)
-      jekyll-seo-tag (~> 2.0)
-    jekyll-theme-leap-day (0.1.1)
-      jekyll (~> 3.5)
-      jekyll-seo-tag (~> 2.0)
-    jekyll-theme-merlot (0.1.1)
-      jekyll (~> 3.5)
-      jekyll-seo-tag (~> 2.0)
-    jekyll-theme-midnight (0.1.1)
-      jekyll (~> 3.5)
-      jekyll-seo-tag (~> 2.0)
-    jekyll-theme-minimal (0.1.1)
-      jekyll (~> 3.5)
-      jekyll-seo-tag (~> 2.0)
-    jekyll-theme-modernist (0.1.1)
-      jekyll (~> 3.5)
-      jekyll-seo-tag (~> 2.0)
-    jekyll-theme-primer (0.5.3)
-      jekyll (~> 3.5)
-      jekyll-github-metadata (~> 2.9)
-      jekyll-seo-tag (~> 2.0)
-    jekyll-theme-slate (0.1.1)
-      jekyll (~> 3.5)
-      jekyll-seo-tag (~> 2.0)
-    jekyll-theme-tactile (0.1.1)
-      jekyll (~> 3.5)
-      jekyll-seo-tag (~> 2.0)
-    jekyll-theme-time-machine (0.1.1)
-      jekyll (~> 3.5)
-      jekyll-seo-tag (~> 2.0)
-    jekyll-titles-from-headings (0.5.1)
-      jekyll (~> 3.3)
     jekyll-watch (2.1.2)
       listen (~> 3.0)
-    jemoji (0.10.1)
-      gemoji (~> 3.0)
-      html-pipeline (~> 2.2)
-      jekyll (~> 3.0)
     kramdown (1.17.0)
     liquid (4.0.0)
     listen (3.1.5)
@@ -198,17 +38,6 @@ GEM
       rb-inotify (~> 0.9, >= 0.9.7)
       ruby_dep (~> 1.2)
     mercenary (0.3.6)
-    mini_portile2 (2.3.0)
-    minima (2.5.0)
-      jekyll (~> 3.5)
-      jekyll-feed (~> 0.9)
-      jekyll-seo-tag (~> 2.1)
-    minitest (5.11.3)
-    multipart-post (2.0.0)
-    nokogiri (1.8.5)
-      mini_portile2 (~> 2.3.0)
-    octokit (4.13.0)
-      sawyer (~> 0.8.0, >= 0.5.3)
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
     public_suffix (2.0.5)
@@ -216,33 +45,19 @@ GEM
     rb-inotify (0.9.10)
       ffi (>= 0.5.0, < 2)
     rouge (2.2.1)
-    ruby-enum (0.7.2)
-      i18n
     ruby_dep (1.5.0)
-    rubyzip (1.2.2)
     safe_yaml (1.0.4)
     sass (3.6.0)
       sass-listen (~> 4.0.0)
     sass-listen (4.0.0)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
-    sawyer (0.8.1)
-      addressable (>= 2.3.5, < 2.6)
-      faraday (~> 0.8, < 1.0)
-    terminal-table (1.8.0)
-      unicode-display_width (~> 1.1, >= 1.1.1)
-    thread_safe (0.3.6)
-    typhoeus (1.3.0)
-      ethon (>= 0.9.0)
-    tzinfo (1.2.5)
-      thread_safe (~> 0.1)
-    unicode-display_width (1.4.0)
 
 PLATFORMS
   ruby
 
 DEPENDENCIES
-  github-pages
+  jekyll
 
 BUNDLED WITH
    1.17.1