Created Contact Implementation class to pass the tests in ContactTest
Updated ContactTest so that it will compile properly.

• Moved declaration of Contact object outside of setUp method and declared it as it static.

• Declared both setUp & tearDown methods as static.

• Renamed setUp & tearDown methods.
Updated testAddNotes method

Updated the testAddNotes test to accommodate for the way I have chosen to separate the notes in the addNotes method in ContactImpl.
Noticed a bug in the ContactImpl class and have added a test to ContactTest to test for this bug in the future.

The addNotes method in ContactImpl was replacing (deleting) old notes rather than adding to them (as intended).

I have extended the testAddNotes method in ContactTest, to insure this is tested for in the future. The ContactImpl addNotes method now fails the new test.
Fixed the bug in the addNotes method so that it now passes the new test.
Tidied up code and added JavaDoc comments.