Embed the intro message into the menu prompt for the actual message, to make it skippable

This still needs tests, but I wanted to see what @emcgee (and @benlangfeld) think about this change..

Instead of playing `Message received on October 5th at 4pm... message received from 111222333` in one controller, then in the next controller playing the message followed by the options (`press 1 to save this message...`), this combines it all into the menu prompt.

This allows the customer to jam the 1 key as soon as it starts to get to what they want to hear instead of being forced to sit through a long stream of canned stuff.  It makes for a much smoother customer experience.

To do this, I had to get the SSML objects into the helper class that creates the message from the `Adhearsion::CallController::Output::Formatter` - not sure if there's  better way to mix SSML types in single `#menu` prompt.