update .gitignore for MacOS files
Add our README as separate file
Add M550 code to spit out some info, including compilation date
Documented Auto Bed Leveling
ABL at any points
Configure for MissionBot as of 2014-02-17

Geeetech Printrboard with Auto Bed Leveling & Z Safe Homing

Touches
    Marlin/Configuration.h
    Marlin/Makefile
    Marlin/pins.h