Ensure all Reporters accept a callback function

This change ensures all reporters accept a callback function for a third parameter of their `run()` function, which is fired when the tests are done.

`browser`, `lcov`, `nested`, and `verbose` needed these parameters.

`default`, `junit`, `tap`, etc already accepted a 3rd callback parameter.

The reason for this change is because of a separate change recent accepted to https://github.com/gruntjs/grunt-contrib-nodeunit, which adds `reporter` and `reporterOutput` options to choose the reporter and an optional output file for the results.  Prior to this change, if the grunt config specified a reporter that didn't accept the 3rd callback parameter, grunt would hang waiting for a callback that never happens.

This is an update (merge-clean) PR of https://github.com/caolan/nodeunit/pull/230