Pass mocha instance as second argument to prepare/unprepare handlers

[krisdages]

I needed to do something asynchronous with the mocha files and test suite in the handlers.

The mocha instance was available in the Mocha.prototype.run override, so I just added passing the instance after the done callback.

[krisdages]

Sorry, I accidentally had put "bump major version" instead of "minor" in the second commit.