Test for implemented the Kata added.
Created the class to test.
The definition of the problem ...
I forgot to add it, but now it's in.
Added the class that implements the countdown
Minor fixes:

   * Changed .gitignore
   * fixed import in CountdownTest.py
Fix: at start, isStopped should return True.
New test added, now we want that when countdown is started the instance of countdown changes its state
Added logic to be able to change the state to started (not stopped)
New iteration, added test so that, when calling decrease counter, and the count is greater then zero, the state is still changed.

Note: there current implementation, of decreaseCounter, is just a stub. We need to add a better test case to check that this is really working.
New iteration, now the Countdown is complete

* Added a new test to ensure the counter has the correct implementation
* Refactored and changed the implementation accordingly so that the Counter works as is should.
Added a final test, to check that the Countdown isStopped when counter is less or equal than zero. Some changes in the code comments, and the name of the test functions were added, in order to be more descriptive