corrected two important bugs (issue #748) in tabs+history 

* when using the ajax effect on the tabs the "initialIndex" setting didn't work
* when using the ajax effect on the tabs with the history plugin, the first tab was loaded anyway, regardless of the value of initialIndex

With this patch any custom effect for the tab plugin that performs asynchronous loading must contain the word "ajax" (the check is case insensitive).

I've tested pretty much all the cases.