Added `can_brew_coffee` permisison to group.

Was just checking if hey were in the group, group now has the
permissions to do so.
finished Servo library
Working on permissions based login
Changed sensing to RAW.
Deprecated some python classes.

Will now use Arduino w/ PySerial to control machine's hardware.
Changed header for machine control abstractions.
Added skeleton for CoffeMachine abstration
Merge remote-tracking branch 'upstream'

Conflicts:
	barista/machine_controls/servo.py