Add 302 Redirect for /code/<project> to https://github.com/18F/<project>

I have not tested this on `staging`, looking to @konklone to deploy and test this out. Expected outcome should be to provide a 302 redirect from `https://18f.gsa.gov/code/18f.gsa.gov` to `https://github.com/18F/18f.gsa.gov`.
How would it even arrive at the 403 line, then...? (This is not holding up the merge, I'm just curious.)