Replaced GLEE with GLEW v1.9.0.

In response to a post on the forums ( https://forum.libcinder.org/#Topic/23286000001378295 ), I have replaced GLEE with GLEW version 1.9.0. This is obviously for Windows only, but I have included the glxew.h file, too.

Glew is statically linked, to avoid having to use .lib and .dll files. In order to do so, I had to change a few #include statements in GLEW's source files from ```#include <GL/glew.h>``` to ```#include "glew/glew.h"``` and add the GLEW_STATIC definition to the preprocessor statements. When updating to a more recent version of GLEW in the future, simply adjusting the #includes should be all that is necessary to make it work.

I have tested this change with most of Cinder's samples, as well as nearly all my own applications. Everything seems to work fine, including shaders and multisampling. I couldn't detect a change in performance, either.

Feel free to close this pull request if you think the time isn't right to change to GLEW. Otherwise, see if it works for you - I can't think of a reason not to include it with v0.8.5.

-Paul