Fixes jshint exit code vows under windows.

This fix uses https://www.npmjs.org/package/exit to instead of `process.exit` and various hacks to accommodate for windows `stdio` strangeness.

This lib is also used by `grunt` as a dependency and has been tested by various people to ensure it works across platforms.

This PR should fix the following issues:

#1541
#1408

References for the windows stdio issues:

joyent/node/issues/3584
https://github.com/cowboy/node-exit/issues/4

Testing `drain` of stdio is not included as this is tested by `exit` package by various contributors and users already.

Lastly, thanks for the awesome work on JSHint!

Best,

AQ