Merge pull request #63 from bvssvni/master

Removed gfx
Updated the dependencies link
Merge pull request #65 from Coeuvre/master

Updated the dependencies link
Add Window.get_size implementation to WindowSDL2

The old method of depending on the default trait implementation was insufficient as the trait used the size the window was constructed with, which is wrong if the window has ever changed size.
Merge pull request #66 from jakerr/get-size

Add Window.get_size implementation to WindowSDL2
Upgrade to latest rust-sdl2