Lazy initialize the FloatBuffer used in toBuffer() method in Mat3/Mat4

instead of allocating it with each new instance! This will create less
garbage and reduces memory footprint.
Merge pull request #4 from bgroenks96/master

Added new Core-JOGL implementations and new CoreShader setUniform system
linear gradient example added
Merge branch 'master' of git@github.com:void256/lwjgl-coregl.git
Modify LinearGradientExample to animate