Add collectionViewClipsToBounds to set the clipsToBounds.

[SuperTango]

On occasion, i've had to make FSPagerCells that have shadow borders that bleed outside of the cell (and thus outside the underlying UICollectionView). This Pull Request adds the ability to set the collectionViewClipsToBounds parameter so allow or disallow this behavior.

[Davidxiaoshuo]

Please publish this submission