(width) and (height) shouldn't be used in setup.

Update docs for these functions. Issue #50.
Merge pull request #62 from nbeloglazov/master

Add mouse-wheel callback. 
Merge pull request #63 from nbeloglazov/patch-1

(width) and (height) shouldn't be used in setup.
remove warnings for using size and width in setup - these should be allowed. If they have inconsistent behaviour, this is a bug.