namespace redis usage (#2869)

* add redis-namespace gem

* namespace redis usage

* refactor redis namespace code to be less intrusive

previously : would be prepended to keys when the
REDIS_NAMESPACE env var was not set

now if it is not set the namespacing functions are
not used at all, which should prevent disruptions
when instances update.

* fix redis namespace variable style in streaming js

* remove trailing space

* final redis namespace style fix

Gemfile

@@ -26,6 +26,7 @@ gem 'doorkeeper'
 gem 'fast_blank'
 gem 'goldfinger'
 gem 'hiredis'
+gem 'redis-namespace'
 gem 'htmlentities'
 gem 'http'
 gem 'http_accept_language'