Spans not fully supported

Spans are shown to work on the advanced demo at https://os.alfajango.com/easytabs/#advanced-demo

Using spans instead of list items with the selector  tabs: "> div > span"  does not show tab content correctly and produces a console error.

Uncaught Error: The specified default tab ('li:first-child') could not be found in the tab set ('> ul > li') out of 0 tabs.

