Merge pull request #60 from ChrisGrant/demoapp

A couple of small fixes for the JSON in the demo app.
Refactoring backbarbuttonitemrenderer to BarButtonItemRenderer
Fixing up the visual test app.
Fixing the defaults.
Separating out the back buttons styles from the normal bar button styles.
Added parsing for the backBarButtonItem and incremented the JSON version.
The slider value was previously set in the get method for the thumb's frame.

This is now set in the gesture recogniser. It didn't make sense to set it in a get method and caused a bug where the thumb wasn't set correctly when the value was set through code or interface builder.
Merge pull request #65 from ChrisGrant/backButton

Back button
First steps towards using JSON Model.
Added the JSONModel. It's working so far, but the state setters still need some work.
Further steps towards making the JSON parsing generic with the JSONModel framework
Fixing the state setter behaviour. Everything appears to work now. Next is fixing the tests...
Tests compile now (still don't pass…)
Fixed the tests.
Fixed the demo app.
Made JSONModel submodule path public
Dependency fix.
Merge pull request #3 from bobrippling/serialization

Made JSONModel submodule path public
Fixed framework build
Finally fixing the tests.