Possible fix for Issue#108 on OS X 10.9

Hi there,

so here is the possible fix for Issue #108 that works for me. The "magic" only happens in Context.cpp, specifically, in method maximumSupportedVersion(). I also removed the "non-fix" in Context::create() where I initially introduced the call to glfwDefaultWindowHints() after the call to Context::prepareFormat().

I tested the fix with all of the examples provided that require an OpenGL version of 4.1 or less (that are all except for the computeshader example and the transparency example). I had to change several version numbers in the shader files to fix problems I encountered. Specifically, as the fix for the context now assumes a minimal available OpenGL version of 3.2 the minimal shader version number must be 150. I also demoted some of the shader version numbers to 410 where possible.

Finally, I fixed some semantic issues my compiler complained about, mainly issues of a different initialization order of members in the ctor-initializer then the order in which they where declared in the corresponding header files.

Best 

Sebastian