rails 3 plugin work

* gem and plugin names are different
* rails_12factor not rails_12_factor

Conflicts:
	hatchet.json
	spec/rails3_spec.rb
only warn once about plugin injection in rails 3
fix specs
use `PluginInstaller` for runtime asset compilation

Conflicts:
	lib/language_pack/rails3.rb
set deprecation notices for runtime assets compilation

Conflicts:
	lib/language_pack/base.rb
fix specs