Remove unused gems from Gemfile

Gemfile

@@ -8,10 +8,6 @@ else
   gem "arel", '~> 2.1.3'
 end
 
-gem "jquery-rails"
-gem "coffee-script"
-gem "sass"
-
 # This needs to be with require false to avoid
 # it being automatically loaded by sprockets
 gem "uglifier", ">= 1.0.0", :require => false