kipper - Update GitHub commit statuses from Jenkins build results

Age	Commit message (Collapse)	Author
2017-11-11	CommitRef::new(): Return `Result`	Teddy Wing
	Eliminate `.unwrap()` by returning a `Result`. The `JsonValue::take_string`s return `Options`, so if they're `None`, just fill the struct with the default for `String`, which is `""` empty string.
2017-11-09	CommitRef::new: Parse `PullRequestEvent` payload instead of `PushEvent`	Teddy Wing
	I had originally written this method to parse the payload from the `PushEvent` GitHub webhook, but I now decided that I'd rather listen to the `PullRequestEvent` webhook. It'll mean less traffic and eliminates the work of updating GitHub commit statuses when they're not really going to be seen.
2017-11-09	CommitRef: Add `owner` field	Teddy Wing
	This field stores the "owner" of the commit on GitHub, in other words, a user or organisation. Storing that information in this struct makes it easier to pass around.
2017-11-08	pull_request.rs: Make `CommitRef` public	Teddy Wing
	I had forgotten I needed to make the struct and its fields public. We need this to be able to use it outside of the module.
2017-11-07	pull_request.rs: Parse JSON payload to create `CommitRef` struct	Teddy Wing
	The test now passes, and we create our `CommitRef` struct using actual values from the parsed JSON. In order to get the branch name, we need the part after the last "/" in the "ref" key. There are a ton of `unwrap`s here, but at least it's a start and it's working now.
2017-11-07	pull_request.rs: Idea to get needed data from JSON payload	Teddy Wing
	Non-working app code, but the test tries to check that we get a structure with the right data given a JSON payload coming from the GitHub PushEvent webhook (copied from https://developer.github.com/v3/activity/events/types/#pushevent).
2017-11-07	Add modules for GitHub and Jenkins interaction	Teddy Wing
	Empty stub modules that will be filled in with the communication code.