Support Swift Bêta 5 + Improvements

This version now support Swift Bêta 5

* Works with your custom cells !
Just customize the completionCellForRowAtIndexPath attribute-function.

* Set maximum elements to select
Just set the attribute maxSelectedElements to any number you want and
if this number is reached, the selection doesn’t work. Additionally,
you can perform a custom action when the maximum is reached.

Animation bug corrected