Use the commit author in messages

[codepuncher]

Would be useful to have a message like codepuncher successfully deployed a new release rather than just Deployment completed successfully.
Or even have another attachment field to show the commit author.

[mike-sheppard]

This PR #7 might need a bit of tweaking, although it seems to be working ok on our projects - hopefully, it's useful to other folks!

Unfortunately, I couldn't find out how to get the current git username (mike-sheppard), so ended up using the full name from: git config user.name