adding success_json, error_json and rescue_from ParameterMissing within ApplicationController.
adding better_errors, rspec and factory girl gems.
adding various files related to rspec.
adding comment model, controller, factory and migrations.
adding comments as nested resource of posts.
now posts controllers has rspec tests
adding comments field to Post model, and its factory girl file.
adding Comment resource to ng app
adding PostDetailCtrl to ng app.