This is a fork of the gem which was before packaged into Ember https://github.com/emberjs/ember.js/tree/v2.18.2
This gem is using an unusual versioning: x.x.x.x. First 3 are the targeted Ember version, and last one is for modifications done to the gem itself.
Change version in lib/ember/version.rb and then run rake
gem build ember-source.gemspec
gem push discourse-ember-source-x.x.x.x.gem