Small api tweaks

 - create `./response` and `./request` so you can do `require("hammock/response")`
 - make `new` optional
 - remove lodash dependency and inline the each usage.
 - allow passing a callback to `MockResponse` instead of doing `var res = ...; res.once("end", cb)`
 - have response emit "finish" as per WritableStream spec
 - rename response `'end'` event to `'response'` event. `'end'` has specific meaning wrt Readable streams and overloading it is confusing. We still emit `'end'` for back compat. consider deprecating it.
 - have `npm test` actually run tests
 - update version numbers in dependencies. This means that when cookies makes a
    breaking change this code will continue to work since it depends on 0.3.x instead of 
   'anything'
 - use tape. It's lighter / leaner / faster to install / has smaller surface API.