Add an ignore-the-errors flag

[alexcouper]

Sometimes, you really want to commit, just to stash it away.

[alexcouper]

This turns out to exist in git already::

git commit -a --no-verify

Docs updated in https://github.com/alexcouper/captainhook/commit/b52ce3cfc076996808dbb9afd6d66a5dbe1cbcbe