Fix helper specs and add spec rake task
Add AssetInstaller to update manifest when copying assets
Add specs for AssetManifest
Curly brace expansion isn't supported by Sprockets (File.fnmatch)
Add methods to asset manifest
Add NullManifest
Add manifest cleanup and specs for AssetInstaller
Fix NullManifest method signatures
Add support for JSON manifests (Rails 4)
Fix specs for AssetInstaller
Use full rubygems URL in Gemfile