Add commit message functionality
Merge pull request #2 from alphagov/edit-summary

Add commit message functionality
Improve README
Show committer details in header

This commit uses the output of `git config` to show the committer
name and avatar in the navbar.

Improves the colour and words of the draft badge.
Add link to 'Recent config changes'
Prevent crash when Jenkins can't be reached
Show success/error flashes when saving