Add 'xcode-select --install' to ## install on Mac (#221)
Add 'xcode-select --install' to ## install on Mac (#221)

Added lines 227 to 231 to remind folk to install gcc / Apple's Command Line for Tools for Xcode if user hasn't either installed.
wroscoe/donkey,wroscoe/donkey,wroscoe/donkey,wroscoe/donkey