Support privately-hosted git servers

[szaydel]

It seems like having support for privately-hosted git and hg servers is not a bad idea. Many organizations rely on having git hosted internally, for any number of reasons, and yet still have same problems that Goop could potentially solve for them.

I run into this with my privately-run Git instance:

=> Fetching [email protected]/sz/sandboxy.git...
goop: unrecognized import path "[email protected]/sz/sandboxy.git"