Make the server function serve without errors.

Fixes issue described in: https://github.com/jedrichards/dotfiles/issues/3

Also swapped order of lines 5 and 6.  If `python -m SimpleHTTPServer $port` runs successfully, the next line will not be executed until you kill the running server.  So with credit to https://github.com/mathiasbynens/dotfiles/blob/master/.functions#L100, open the browser with a delay and in the meantime run the server.