Merge pull request #527 from bvssvni/master

Simplified condition in update loop
Merge pull request #531 from bvssvni/master

Fixed edge cases in rendering
Merge pull request #533 from bvssvni/master

Updated doc examplee for `GameIterator`
Merge pull request #535 from bvssvni/master

Set `last_frame` directly
Add a comment to the explicit continue in NoEvent

As mentioned in https://github.com/PistonDevelopers/piston/issues/528
Change sleep to use std::time::duration::Duration

This fixes a compile error.
Merge pull request #540 from imbaczek/master

Change sleep to use std::time::duration::Duration