Updates

-Added assimp for handling models in the future.
-Added GLEW for handling OpenGL extensions.
-Added stb_image for handling images for textures in the future
-Updated the game_state class to have the GLEW header, stb_image and the
shader_program class included by default.
-Updated the game_state class to have a deconstructor that destroys the
tiny_state in it.
-Updated the game_state's keyCallback method to __stateUseKeyCallback to
avoid duplication of the method in the future.
-Updated the game_state class to call glfwPollEvents when updating the
state, and glfwSwapBuffers on the window object when rendering.
-Added a shader_program class to handle loading and using shaders and
creating programs for their use.
-Updated the test state to use a simple shader
-Added simple vertex and fragment shaders.
-Updated the main program to include the GLEW header before the OpenGL
header.
-Updated the main program to use a window for debugging mode and
fullscreen for release mode.
-Added GLEW initialization to the main function for the program.