fixed pixel order of glimread

Hi, 
I found a bug in the glimread function.
Hope I did everything correctly, this is my first pull request on github ;)
There are more errors in the aux.jl files for all OpenGL versions bigger than 1.0.
Seems, that the error is, that you import OpenGL functions which are deprecated in OpenGL > 1.0.
Also you don't import Images.imread. 
But that would mean deleting nearly all of the aux.jl, which I don't feel very comfortable with in this stage :D 
Cheers,
Simon