Fixed renderer on osx

- My Macbook Air only supports OpenGL 2.1... dang
- Anyway, I added some ifdefs to handle both the 2.1
  and 3.3+ cases
- Shaders are different, obviously, but once these move
  to materials it will be easier to manage
- No vertex array objects in 2.1, but the code is still
  there and remarkably easy to #ifdef out in the 2.1 case
- So, looks like we'll support both flavors, which is
  a good thing in that the iOS will only have ES 2, I think.