I've made a couple of quick changes:

• The deployments API has now been released so we don't need to send a special Accept header to use it anymore
• I felt that the update method was a bit misleading/unclear. Per this page:

Once a deployment is created, it cannot be updated. Information relating to the success or failure of a deployment is handled through Deployment Statuses.

As a result, I've renamed it to updateStatus to try and prevent confusion.

• I've added a few more doc blocks and links to GitHub's dev docs. Nothing too major.
• Added a new function for getting all of the deployment status updates for a given deployment.

As for the tests:

• In the spirit of the other tests, these work by mocking the API client and expecting certain functions to be called.
• I haven't added any functional tests since they appear to be disabled in the PHPUnit config file and I'm not familiar enough with the project to understand if these are required or not (they're not present for some other APIs).

In terms of documentation:

• I've added a markdown file for the API and linked it from the main list.

Thanks for your existing work on this, the existing code was nice to work with. Hopefully this can be pulled into knplabs/php-github-api soon.