Upgrade to OpenGL4

[Lunanne]

Includes the addition of GLM & GLEW. Didn't realize Deledrius was also working on that so it's probably best to wait with merging until after.

[Deledrius]

After rebasing this to work from master, it compiles and runs, but the window only flashes briefly: the program exits through the "Failed to initialize GLEW" error path.

[Deledrius]

Upon further debugging, the GLEW error string returned is "Missing GL version". If I change the SDL_GL_CONTEXT_MAJOR_VERSION to 3 rather than 4, I finally receive a rendered screen containing the credits.

Looks like this is caused by a lack of support on my system for OGL 4.3, so I can't test the debug portion here.

[zrax]

After doing some research, I found that SDL2's bundled cmake modules are very different depending on whether it was built with cmake or autotools. I feel like including a full FindSDL2.cmake is overkill for fixing this, so I may try to create a simpler solution to handle both versions in a separate Pull Request.

[Lunanne]

@zrax is there a name for the specific indent style that you want? I'm having trouble configuring Clion to format it correctly and I would like to save us some time in the future