Update Angular version to 1.2.12 (Closes #42)
Remove directions for unstable branch since we are no longer maintaining it
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Fix detection of Rails::Engine for Rails 4

There was code saying if defined?(Rails::Engine), but that didn't work on our Rails 4 project.
It seems to work better as defined(::Rails::Engine).
javascripts directory is plural
Merge pull request #46 from bwalding/master

javascript assets path should be the plural - javascripts
Merge pull request #45 from tjgrathwell/colon-colon-rails-engine

Fix detection of Rails::Engine for Rails 4
Bump to version 1.2.13 (closes #50)
Bump version to 1.2.14 (closes #51)
Bump version of Angular to 1.2.15 (closes #52)
Upgrade version to 1.2.16 (closes #53)