Merge pull request #788 from bvssvni/master

Pointing sdl2 to crates.io
Merge pull request #790 from bvssvni/master

Upgraded to latest piston-current
Merge pull request #791 from bvssvni/master

Fixed Travis CI
Merge pull request #792 from bvssvni/master

Added `DANGER` to `render_2d_opengl` and `render_2d_gfx`
Merge pull request #793 from bvssvni/master

Reexported `DANGER`
Removed `rustc/cargo -v` from .travis.yml

See https://github.com/PistonDevelopers/piston/issues/794