Options to set explicitly wrapper width and height added. Fixes #45

Hi cubiq,

just found a solution to issue #45. 
When a new Swipeview object is instantiated and the html wrapper element is not rendered, you can prevent wrapper size to be === 0 setting explicitly `wrapperWidth` and `wrapperHeight` options. 

I think it’d be worthwhile to pull it into the project repository.

Thanks!