Initial work on hubot notifications.

Mostly remove any reference to room_id. Renamed to room as a string.
See #71.

Signed-off-by: François de Metz <francois@stormz.me>
Add hubot chat_service.

Signed-off-by: François de Metz <francois@stormz.me>
Some doc about the Hubot adapter.

Signed-off-by: François de Metz <francois@stormz.me>
Ruby 1.8 hash style.

Signed-off-by: François de Metz <francois@stormz.me>
Update install instructions with config/environment.rb.

Signed-off-by: François de Metz <francois@stormz.me>
Accept pull req events / pass JANKY_COMMIT_URL

- JANKY_COMMIT_URL is now pushed to Jenkins jobs as parameter
- Hook registration establishes pull_request event
- Payload parser now speaks pull request event
- Add API support for repos/#{nwo}/pulls/#{number}/commits
- Be resilient to GitHub messing with the API results -
originally it was commit["commit"]["message"], then commit["message"],
and then commit["commit"]["message"] once again
Added JANKY_GITHUB_EVENT_TYPES configuration

 - Allows for configuring whether Janky responds to pull_request or
 push event types or both
 - Added parsing of the user provided values to ensure only the
 appropriate ones are allowed
 - Corresponding docs
Include Jenkins URL in ChatService.speak
Added start messages to chat service

It's incredibly useful to know that Janky is succesfully handling
build requests based on GitHub notifications.