Preview enigma responses

You can now preview your enigma response before submitting it. This should help with testing out any special text formatting, especially when using the [code] tags.

Unlike many preview buttons, this does not rely on Javascript, so is usable by everyone. Of course this means it will cause more strain on the server, but I'm sure the server can cope. However, if the site were to have hundreds of users posting at the same time, then it may become a problem, but I think for now we are safe.