Require the ruby racer only in production since installing it on dev machines...

Require the ruby racer only in production since installing it on dev machines can cause a lot of problems. Hat tip to Jeroen van Baarsen

Gemfile

@@ -169,7 +169,6 @@ gem 'semantic-ui-sass', '~> 0.16.1.0'
 gem "sass-rails", '~> 4.0.2'
 gem "coffee-rails"
 gem "uglifier"
-gem "therubyracer"
 gem 'turbolinks'
 gem 'jquery-turbolinks'
 
@@ -254,6 +253,7 @@ end
 
 group :production do
   gem "gitlab_meta", '7.0'
+  gem "therubyracer"
 end
 
 gem "newrelic_rpm"