Handle push options
This MR enables the
post_receive hooks to handle the newly-introduced Git push options.
The immediate goal is to enable
git push -o skip-ci ... functionality. This implementation however, is not tied to
skip-ci and pushes all of the push options to GitLab to handle.
gitlab-shell is in the middle of moving from using Redis to an internal API for handling the post-receive hook (see #77 (closed)). This implementation only passes the push options using the new internal API.