Get author and committer from a config variable or default out.

[ishworgurung]

Neat idea. I think, for dura auto-commit vs. a human commit, it'd be nicer to distinguish the author and committer.

dura/src/snapshots.rs

Line 54 in c5c49d3

&head.author(),

[tkellogg]

oh yes! It could be something like dura@github.io. I'm not sure about the benefits of having the email be a real email address though.

[eauxpie]

also being able to use the git configured author instead of whoever the author of head was. I don't need to distinguish dura commits from my other commits, but I do want them to show up consistently as mine, not whoever last pushed to that branch

[tkellogg]

A good approach would be

1. Default to the settings of git config
2. Override in the config file

Details around the config file are being hashed out in #25, but we can easily take approach \1 now.