Added unit tests

Hey!

Finally I managed to get some time to push iOS tests.
I'm using XCTest, the framework included in XCode5 for unit testing. I seems to be the best option right now although we've got a lot of other options (gh-unit, OCUnit, SenTestingKit, Kiwi...)

I followed Android tests design, using a real server and added/removing elements during the tests.

Looking forward your feedback!