Add issues command, which opens github issues for a repo

Just came up with this command, I think it's gonna be great!

While you're in a git repo on your command line, you run `issues` and it opens the github issues for that repo in your browser.
That makes sense.

I think that scripts in this repo should be able to share code, especially for simple/common plumbing like parsing `git remote -v` (this is the 3rd script in this repo that would be doing that). They already do in a few ways that I would be loathe to rip out, and I anticipate that sharedness increasing as we potentially add more and more advanced capabilities.

Luckily, we have tools to make this basically arbitrarily unobtrusive. Having an install script that basically did `echo "source $repo/.git-rc" >> ~/.bashrc`, or just `echo "export PYTHONPATH=\"\$PYTHONPATH:$repo/util\"" >> ~/.bashrc` is a pretty low barrier, and common / table stakes for things of this sort, so I'd be up for adding such a thing.