Add links to How-To guide app in appropriate places in docs

[leggetter]

We have a "How-To" app. The point of this app is to provide concrete demonstrations of achieving common use cases using BRJS.

The app currently contains:

• Internationalisation
• Routing

The point in this issue is to ensure:

• The how-to app is reference from appropriate places in the docs
• The how-to app is in a good state e.g. does the internationalisation example need tidied up?