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
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
Enable Travis & Vagrant, for 1-step compile locally and on CI server

Teensy cores are installed from our private Amazon S3 bucket
Use Z_SAFE_HOMING_FIXED_POINT to keep the bed from crashing into the extruder

For when Z-homing is only safe in certain pre-defined places.

Adds logic to G28, G29, and G30.
slow down z homing
invert E direction
tweak z probe offset
Git required for tests to run
Custom M-codes, Z probe offset

Add custom M code for changing Z probe offset

Refactored code values into Configuration.h, and changed numerical value for
info-report so as to not conflict with any documented codes
test runner filter uses -w to match whole words
Use dependencies release from GitHub instead of S3
re-set 3pt ABL probe points for our printer