fix (tooltip): Tooltip's content-template option throws errors in Firefox 10 re:#846

The tooltip directive gets the content-template then attempts to replace the content div
with the template html. The function which does the replacement returns the modified
HTML for the templateEl. The function returns `templateEl[0].outerHTML` but `outerHTML` is
not supported in Firefox until v11. I have included a shim which handles the case where
`el.outerHTML` is not defined

no breaking changes