Created COMMITTERS.md file

#8 earlier pull request, addressed all comments from there. 
As I think about it, I think I agree. We can document any needed internal process on a branch on our internal fork of this repository.

The thought here was that some internal contributors might be daunted at first to come out here to work in the open public, so I just wanted to make the point that all of the internal facing tools are still available for people to use if they so choose / are comfortable, but maintaining the overall point that this public repository is the source of truth, and must be logged here first.