Converts asset_host to an ENV variable

Author: cbaudouinjr

config/environments/production.rb

@@ -32,7 +32,7 @@
   # `config.assets.precompile` and `config.assets.version` have moved to config/initializers/assets.rb
 
   # Enable serving of images, stylesheets, and JavaScripts from an asset server.
-  config.action_controller.asset_host = 'https://staging.brickhack.io'
+  config.action_controller.asset_host = ENV['ASSET_HOST']
 
   # Specifies the header that your server uses for sending files.
   # config.action_dispatch.x_sendfile_header = 'X-Sendfile' # for Apache