using sprockets-rails instead of quiet-assets

Gemfile.lock

@@ -338,8 +338,6 @@ GEM
       coderay (~> 1.0)
       method_source (~> 0.8)
       slop (~> 3.4)
-    quiet_assets (1.0.2)
-      railties (>= 3.1, < 5.0)
     rack (1.6.4)
     rack-openid (1.3.1)
       rack (>= 1.1.0)
@@ -597,7 +595,6 @@ DEPENDENCIES
   piwik_analytics (~> 1.0.1)
   poltergeist
   prawn_rails
-  quiet_assets
   rails (~> 4.2)
   rails-assets-bootstrap-markdown!
   rails-assets-date.format!
@@ -624,6 +621,7 @@ DEPENDENCIES
   sass-rails (>= 4.0.2)
   shoulda-matchers
   spring-commands-rspec
+  sprockets-rails
   sqlite3
   stripe
   stripe-ruby-mock