Glium frontend for the glyph-brush text renderer.

It bases on the gfx_glyph crate. While it works, some docs are still missing, and maybe one API call or two. I've written it mostly to scratch a personal itch of mine. If you find something to be missing, file an issue or send me a PR!

TODO:

• examples and docs are still about the gfx-brush crate
• mode for crisp text rendering (exposing texture interpolation commands send to glium)
• mode for crisp text rendering (making rusttype not "alias", might need changes in glyph-brush)