Gruntbuild + general clean-up

This is iteration 0 before porting the lib to browser.

1. I've added ``grunt`` build system, to simplify testing and linting.
2. Corrected all linting issues (interface of function changed a bit).
3. Updated readme.
4. Added cross platform ``md5`` implmenetation, could be used both node and browser.
5. Created a small helper for query strings, to avoid ``querystrings`` dependency.

As you merge it, try ``npm install`` and ``grunt`` :)