Merge pull request #2 from pradeepcodes/fix-osx-dylib

Fix SDL dylib filename in configure for OSX
Silence a few warnings.
Enable Travis build. made README support markdown to render travis link. Travis currently only builds for OSX but can be extended for other platforms
Merge pull request #3 from pradeepcodes/travis

Enable Travis build. made README support markdown to render travis link....
Add various routines for working with pixel formats/rgb mapping
Wrap 'SDL_MapRGB'