Revert "Remove the `:coffee` and `:coffeescript` Haml filters"

This reverts commit ae7de2f8.

config/initializers/haml.rb

 Haml::Template.options[:ugly] = true
-
-# Remove the `:coffee` and `:coffeescript` filters
-#
-# See https://git.io/vztMu and http://stackoverflow.com/a/17571242/223897
-Haml::Filters.remove_filter('coffee')
-Haml::Filters.remove_filter('coffeescript')