exmpp: 0.9.9 - Erlang modules for XMPP/Jabber development

created new formula for Exmpp

There are two closed pull attempts for this, but I don't see a reason in either why this shouldn't be added to Homebrew: [9495](https://github.com/mxcl/homebrew/pull/9495) and [9417](https://github.com/mxcl/homebrew/pull/9417)