Add '.rbxs' extension for Lua files
Add OpenGL shading language (GLSL)

This is the language used for writing OpenGL shaders, which are becoming much more mainstream lately.
Add OpenGL Shading Language.
COPYING is added to excludes as a file that contains copyright information.
Merge pull request #626 from dzidzitop/patch-1

COPYING is added to excludes as a file that contains copyright informati...
Merge pull request #512 from mark-otaris/patch-1

Add the .rbxs extension for Lua files
Merge pull request #599 from larsbrinkhoff/glsl

Add OpenGL Shading Language.