deleteMilestone method
Deletes a milestone.
API docs: https://developer.github.com/v3/issues/milestones/#delete-a-milestone
Implementation
Future<bool> deleteMilestone(RepositorySlug slug, int number) {
return github
.request('DELETE', '/repos/${slug.fullName}/milestones/$number')
.then((response) => response.statusCode == StatusCodes.NO_CONTENT);
}