Added GLFW3

GLFW3 for windows is working.

Linux FindGLFW3 needs to be verified.

Removed all OS specific source including SDL.
first round of fixes

FindAwesomium and AWESOMIUM_LIBS added/fixed
OS.h include wglew.h is now guarded from *nix
removed Sigma_LIBS from cmake (unused)
ADDITIONAL_LIBS is now ADDITIONAL_GLFW_LIBS in cmake
compiles and runs on ubuntu 13.04

- glewExperimental = GL_TRUE
- X11 and other odd GLFW dependencies linked in cmakelists
spaces changed to tabs in CMakeLists
Removed ADDITIONAL_GLFW_LIBS from cmake

danix is right that building GLFW as a shared library removes the need for manually linking X libraries
also, I had missed an "awsomeium" typo. fixed.
Enabling DEPTH_BUFFER_TEST; fixes depth buffer issues
Merge pull request #69 from wrongu/depth-buffer-fix

Fixed depth-buffer problem
Merge pull request #67 from wrongu/glfw

Linux + glfw (ubuntu 13.04)
Support the GL Core Profile on OS X.  Do not use glew on OS X.
CMake lists and modules support OS X.
Workaround an issue with makefile generation on OS X.

Workaround an issue where the generated makefile may not include the
necessary flags for finding Awesomium.
Add OS X installation instructions to the ReadMe.
Merge pull request #70 from DeVaukz/glfw

Add support for building and running on OS X.
Makes to work with Awesomiun 1.7 in Linux Ubuntu 13.10
Merge pull request #74 from Zardoz89/glfw

Makes to work with Awesomiun 1.7 in Linux Ubuntu 13.10
Fixed linux builds

The CMake file was errantly setting GLEW_LIBRARY in the linux section. This was causing a failure in find_package(GLEW). The setting to a dummy value was moved to the Mac section as Mac doesn't use GLEW.
Merge branch 'glfw' into develop