Initial commit.

Implemented Tutorial 1 from http://www.arcsynthesis.org/gltut/ using glfw 3.0.1 and Xcode.
Added Scene destructor to cleanup gl resources.
Added realtime window resizing.
Maintaining aspect ratio viewport, centered on the screen.
Moved specific tutorial code to subdirectory.
Added first part of tutorial 2.
Added part B of tutorial 2.
Added proper attribution and MIT copyright.
Merge branch 'master' of https://github.com/rsanchezsaez/gltut-flgw