Adding platformio building (+ bumped the version again)

We got a nice PR to add platformio build support. See http://platformio.org/

Installing on Mac with Homebrew is very easy:

brew install platformio

Consult the platformio site for other systems or if you want to know the details.

The following is for reference (tested with OS X), which is grabbing the newest devel even if it was force pushed. It keeps your latest config files. As you are using git you can easily check with git diff, what has changed in the case that the compilation stopped working.

cd <your skynet github installation>
# backup our config
cp Marlin/Configuration.h /tmp
cp Marlin/Configuration_adv.h /tmp
# update from Github
git fetch
git checkout SkyNet3D-Devel # or the branch you use (like SkyNet3D-V2.4.x)
git reset origin/`git rev-parse --abbrev-ref HEAD` --hard
# restore the config
cp /tmp/Configuration.h Marlin/
cp /tmp/Configuration_adv.h Marlin/
# build and upload the new skynet
platformio run -d Marlin -t upload