$.find: added indexOf checking form jqmData selector to improve speed on non-jqm selectors

jQuery Mobile added ":jqmData" selector by decorating the standard
$.find method with a regexp for every selector supplied in the
method. But not every selector is a ":jqmData" selector so that
hit performance. I've added a simple indexOf check is faster
then always replacing contents in a selector; when the ":jqmData"
selector is found, then te regexp replace will occur.

Please refer to test on jsperf:
    http://jsperf.com/jquery-mobile-find-patch-performance-fix