added wrap method for added wrapping block with overflow: auto

[everyonesdesign]

useful for high big height dialogs the code looks a bit tricky but it's really cross-browser, and it's difficult to add this feature without changing the code a lot (or maybe rewrite it to add a wrap always? it'll do the styling options more flexible). last example added uses that feature. it the pull request is merged, docs have to be updated.

[everyonesdesign]

demo can be found here http://everyonesdesign.github.io/dialog/ (last dialog)