Updated README

Signed-off-by: Jacky Boen <aqiank@gmail.com>
Merge pull request #32 from TomMurray/master

Add darwin cgo build commands for Mac OSX targets.
Updated README

Signed-off-by: Jacky Boen <aqiank@gmail.com>
Merge branch 'master' of https://github.com/jackyb/go-sdl2
added pixel format
Merge pull request #33 from krux02/master

added pixel format
Updated cgo directives for Mac OS X
Updated readme
Updated readme
Fixed typo in include
Merge pull request #34 from iand/master

Support OS X build
Add WINDOWPOS_CENTERED constant