@saleem: Added two more tests to verify interactions between Alarm and Sensor; changed sourceCompatibility to Java 1.7
@saleem: Added new test class AlarmTestUsingCustomMock to demonstrate the how verbose code gets if a custom mock class is used
@saleem: removed unused code from custom mock class
Merge pull request #18 from saleem/master

@saleem's additional unit test for the Tire Pressure Monitoring System, using a custom mock class