Handle response when not ajaxy

[jamezpolley]

The current way of handling responses assumes that the user has a fancy browser and used ajax to submit the form, and just sends back a fragment to load into the containing div.

Instead, the handler should detect cases when this did not happen (hint: missing an extra value that only gets passed if the ajax magic worked) and instead redirect the user to the right page (/events, /, or /event/id, depending on where they came from)