Fix background color of WebView

The WebView had a white background color and looked out of place with the
off-white used in the app.  Switch it to transparent, which apparently must
be done after the content is loaded.
Add "Up" ActionBar navigation from the Details Views

This has some serious shortcomings; notably I'm not doing anything with
saved state, so the list is empty when you use that to return.  These
activities could probably be moved into Fragments anyway.
Update walk-through

No actual user stories completed today :-(.  Shame neither Paypal nor Parse
SDKs could be simply added.  Java dependencies are such a cluster'.