Allow request module override

[cpsubrian]

Relating to #15

These changes accomplish a few important goals:

• Allow apps to override the request handler.
• Pull request parsing out of the api modules.
• Options passed to the request handler more closely conform to node core's url spec.

This allows 'userland' add-ons such as memcached protocol support.

I've taken care that all tests pass with NO changes to the tests themselves (no API changes).

[coveralls]

Coverage increased (+0%) when pulling aab916f on TerraEclipse:refactor into 2bf522b on ncb000gt:master.

[brozeph]

This is looking very clean! Merging, rev'ing and publishing...