Hack to support the nouveau driver (accelerated Open Source driver for nVidia cards) for older cards.
Lowered the required OpenGL version from 3.1 to 3.0.
Lowered the required GLSL version from 1.40 to 1.30.
Merge pull request #87 from TheJosh/support_nouveau

This broadens the range of cards supported.

Lowered the required OpenGL version from 3.1 to 3.0.
Lowered the required GLSL version from 1.40 to 1.30.

Very little actual code was changed, only the version checks.

Tested on Linux and Windows.
Tested on NVidia official, NVidia open source, AMD (unknown) and Intel integrated.

This relates to task #86