Use function version of print() for Python 3 compatibility.
Avoid hard-coded path to Python interpreter.
Merge branch 'python3' into no-hardcoded-python-interpreter

Conflicts:
	bin/ard-reset-arduino
Use function version of print() for Python 3 compatibility.
Merge branch 'no-hardcoded-python-interpreter' into next
Define clean as a "::" goal so we can extend it.
Add a few new flags used in the 2014 releases of chipKIT build tools.