Update mruby to the latest commit, that fixes the require problems
Add a Shader class.

It actually represents a shader program (vertex + fragment shader,
or only one of those). Later, this will be suppliable per-model.
Add the GLM library v0.9.4.4.
Initial shader implementation.
OpenGL legacy code cleanup.
Clean up mruby code (no need for a permanent context).
Remove oldGL leftover.

Matrices are now manually managed, so naturally when we implement
the model view matrix it will not need this.
Forgot to commit the quad shaders.
Separate glfw window calls into a Window class.
Properly translate the model matrix for world position.

Removes more legacy gl code.
Merge branch 'shaders'