Configure all Mob Members in the Beginning

[danytulumidis]

I would like to add a feature to give it a slice of names of the team working right now and then use this to randomly pick the next typist.
Our team would really like and need this feature because right now we use a online wheel to pick the next typist which interrupts the flow a bit.

Maybe as a command line argument and when its set it will use the slice to pick one and if not set use the current committer logic.