Merge pull request #451 from bvssvni/master

Added mouse scroll
Merge pull request #452 from bvssvni/master

Changed `pub use X = mod::X` to `pub use mod::X` in 'lib.rs'
Merge pull request #453 from bvssvni/master

Removed lifetime on `GameEvent`
Deriving `Clone` on Args, `GameEvent` and `GameIteratorSettings`

Closes https://github.com/PistonDevelopers/piston/issues/448