Adds GitHub Pages link.
Adds `respond/3` to `Charlotte.Handlers.HTTP`

This allows for more control over the exact response that is returned to the client.
Adds `respond/4` to `Charlotte.Handlers.HTTP`

This function allows adding custom headers to the response.
Version bump for `respond` spike.
Merge branch 'master' of github.com:LeakyBucket/charlotte
Actual version bump for `respond` spike.
Cleanup `Charlotte.Handlers.HTTP` tests.
Basic logging behaviors.

* Adds `Charlotte.Logger`
* Adds request lifecycle logging to `Charlotte.Handlers.HTTP`
* Adds `request_id` to `Charlotte.Conn` in the form of a `UUID`