Fixed issue with .Matches() public method.

.Matches() and .On() public methods now will both return a boolean
representing whether or not the passed in query is currently active. This
prevents unnecessary calls to the .Matches() method if someone plans on
setting event listeners anyway. Updated a test to make sure it's working
correctly and the .Matches() method is removing the test element once it
is finished running the test. Updated the readme to be a bit more
comprehensive about what this library is useful for.