Add a Project model, persisted in database

Hook URLs are now differentiated by project.
The new URL format is: /hooks/:project_id/:service_name
Make the actions list more dynamic

This change will permit the implementation of dynamic triggers.
Add a Trigger model to link projects and events
Add an action_name validation on Trigger

Also adds a no-op action to facilitate testing.
Add user interface to manage projects and triggers

Also add HAML and Bootstrap CSS using Sass.
User interface is tested via capybara.
Javascript usage is limited to destroy buttons confirmations.