added availability and other methods to Timeslot and Assignment models
fixed response for timeslot create endpoint to include correct availability and customer_count
added logic for GET /api/timeslots endpoint
added 2 tests for GET /api/timeslots endpoint
added FactoryGirl and Faker gems along with factories.rb file
added route and logic for POST /api/assignments endpoint
added 3 tests for POST /api/assignments endpoint
added logic for POST /api/bookings endpoint
added 4 tests for POST /api/bookings endpoint
added after_filter method to applicationController to set access-control-allow-origin header to allow localhost:3333