Suggestion for key metrics

[alexellis]

Hi,

I used this exporter a year or two ago, but revisiting it now I can see a few things missing which I'd consider essential info:

• # commits
• # contributors

Would you be interested in adding this or accepting a PR?

Alex

[kpachhai]

I wanted this capability so I went ahead and worked on it for my personal use. I have submmited PR. Hopefully it can be reviewed and merged into master branch.

#39