Renamed argument "err" to "failureCount" in runner.run callback and in mochaDone to prevent misleading interpretations of argument "err" and "errCount". In my opinion "failureCount" is a better naming because it makes clear that it is type of number and not an Error. Also "failureCount" is closer to mocha's context, because it is also called in mocha's code "failure".
If there is an error within mocha's describe blocks it will be never caught or displayed anywhere and web drivage hangs without telling you what is going on. This behaviour can be easily reproduced by throwing an random Error within describe blocks.
This fix will in case of an Error quit browser, kill selenium and end grunt task with a fatal error.
Merge pull request #1 from peerigon/fix-error-reporting

Fix error reporting