* Dropped the unnecessary SDL2_image dependency.
* Included Linux dependencies in README.
* Reformatted the README.
Facepalm.
Merge pull request #25 from danix111/develop

Linux fixes + misc. tweaks
Merge remote-tracking branch 'upstream/develop' into develop
reduced mars image file size
addressing pull request issues, namely:

* minimal includes in header. no unnecessary includes
* Vector3f changed back to Vertex

Note that this still only applies to GLMesh, GLIcoSphere, and GLCubeSphere so far