Items with spaces can be added infinite times on multiselects
Add optional parameter transformVal that allows the user to define transformation for splitVal

Example demos:
(Infinite spaces, default transformVal):
http://jsfiddle.net/DV23t/9/

(No infinite spaces, transformVal = function (x) { return x; }):
http://jsfiddle.net/DV23t/12/
Merge pull request #2665 from bor0/master

Items with spaces can be added infinite times on multiselects