Khan/KaTeX — pull request #144 by rguthrie3 (2014-10-01 16:19:45+00:00)
Title: Added \forall, \exists, \nexists, \implies, \iff, and \span

Added these symbols and tested. I will continue to add symbols as I think of them, but I went ahead and submitted a pull request because these symbols (with the exception of span) are very important and they don't seem to be present.