allow to specify particular elements within <td> to limit search to

Hi, I was using this plugin for table row filter. and Within my table, in each <td> I had text to display as well as some hidden text as well, hidden input "select option" element. So while searching it was matching the hidden text within "option" tag that I didn't want. 
So I modified the function uiTableFilter to take an additional argument tdElem, that let user to specify a particular elements within <td> to limit the search to. in my case, tdElem was "td span" as i just to wanted to search from text within "td span" elements not "td select" and others.
I think it'll be useful to others as well, so sending the pull request. Please let me know if any concerns. Thanks!