make git clone only fetch last commit on each branch

Cloning will be faster and I do not think it is necessary to go deeper.
Check comment setting. Disable Github spam
Read comment setting from frig.yml
Merge pull request #14 from webkom/comment-settings

Comment settings
add defaults to the webhook setting

This should make sure that keyerrors don't get raised when a repo has no
webhooks.
add sending of webhooks after a build
Merge pull request #13 from relekang/clone-depth

make git clone only fetch last commit on each branch