Set up AngularJS

* added Angular .js files in vendor/assets/javascripts
* added new files and directories for Angular-related controllers and routing:
  * app/assets/javascripts/controllers
  * app/assets/javascripts/directives
  * app/assets/javascripts/filters
  * app/assets/javascripts/services
  * app/views/main
  * main/index.html.erb
  * main_controller.rb
  * mainIndexCtrl.js.coffee
  * mainPostCtrl.js.coffee
  * main.js.coffee
  * assets.rb
  * public/templates
  * mainIndex.html
  * mainPost.html
* edited for Angular-related controllers and routing:
  * routes.rb
  * production.rb
  * views/layouts/application.html.erb
* included dummy ipsum for 'posts'