Move to a docker-compose setup

Gemfile.lock

@@ -40,7 +40,8 @@ GEM
       sassc (> 2.0.1, < 3.0)
     jekyll-watch (2.2.1)
       listen (~> 3.0)
-    kramdown (2.1.0)
+    kramdown (2.2.1)
+      rexml
     kramdown-parser-gfm (1.1.0)
       kramdown (~> 2.0)
     liquid (4.0.3)
@@ -50,13 +51,14 @@ GEM
     mercenary (0.3.6)
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
-    public_suffix (4.0.3)
-    rb-fsevent (0.10.3)
+    public_suffix (4.0.4)
+    rb-fsevent (0.10.4)
     rb-inotify (0.10.1)
       ffi (~> 1.0)
-    rouge (3.17.0)
+    rexml (3.2.3)
+    rouge (3.18.0)
     safe_yaml (1.0.5)
-    sassc (2.2.1)
+    sassc (2.3.0)
       ffi (~> 1.9)
     terminal-table (1.8.0)
       unicode-display_width (~> 1.1, >= 1.1.1)
@@ -72,7 +74,7 @@ DEPENDENCIES
   jekyll-feed
 
 RUBY VERSION
-   ruby 2.6.5p114
+   ruby 2.7.1p83
 
 BUNDLED WITH
    2.1.4