[fix bug 975099] Australis /firstrun and /whatsnew onboarding tour for beta

Please test in the latest version of Nightly.

There are three variations of the same tour:

`firefox/29.0/whatsnew/`
`firefox/29.0/whatsnew/b/`
`firefox/29.0/firstrun/`

`/whatsnew/b/` is a second variation of the whatsnew tour for a GA experiment.

Gareth has already verified the GA events are working correctly on demo3.

This is going out to `en-US` users only for Beta release.