Merge pull request #5 from puiesabu/W2-CRUD

merge Week2 crud implementation
Fixed saving a persisted document using #save
Add travis-ci mongodb service
Merge pull request #6 from oa414/add-travis-ci-mongodb

Add travis-ci mongodb service
Implement MyMongoid Lifecycle Callbacks
Implement define_callbacks
Implement Callback Class
Implement CallbackChain
Implement set_callback
Implement run_callbacks
Implement Around & After Callbacks
Remove unused code: sort_callbacks
Implement Callback#compile
Implement Compile Before Callbacks
Implement Memoize Compilation
Implement Compile Around Callbacks
Implement Compile After Callbacks
Execute run_callbacks with compiled callbacks
Merge pull request #7 from puiesabu/W3-callbacks

Week 3 exercise: callbacks
Use Person model in rspec