delete requests don't support data

[Velyks]

https://github.com/iangreenleaf/githubot/blob/afc9326f76c8e9f6c8401ffde6c649143627463b/src/githubot.coffee#L80

DELETE requests should support data as github expects data with some DELETE requests (https://developer.github.com/v3/repos/branches/#remove-required-status-checks-of-protected-branch)