Add rough code for `update_commit_status`

This new function will make a request to the GitHub REST API to update
the status of a commit using the given arguments.

* Create a new `github` module for this to live in.
* Uses `mockito` to check that the request was made.
* The `API_URL` is necessary in order to set up 'mockito' to work
  properly. That pattern is lifted from an example in the crate's docs:
  http://lipanski.github.io/mockito/generated/mockito/index.html#example
* Sort of make a POST request to the GitHub API to update the status.
  This doesn't actually work, though, of course, as it's incomplete. For
  one thing, we haven't even included the 'reqwest' library, and for
  another we need a way to get the GitHub owner name to build the API
  URL.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 204a45b..add79dd 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,3 +1,4 @@
 mod pull_request;
+mod github;
 mod jenkins;
 mod af83;