allow testing git repo outside of project root

[bewest]

I want to use this module to help report version of my software running in M$'s Azure. Azure is a pretty nice environment, but the wwwroot (where the code was deployed and runs as the CWD), is actually a sibling directory to the git repo root, repository. This patch allows specifying an alternate git root directory to hep with cases like that.

[tblobaum]

@yetithefoot I havent worked on this module in a while. I'll try to find the time to look into this

[OmgImAlexis]

@tblobaum can you please look at this soon as this makes using the package in child dirs completely unusable.