Store application state in local storage

[hjst]

In addition to stashing the current pattern in the URL hash, it can be stored in HTML local storage. This will allow:

1. Saving state between app loads when running as a web app in iOS.
2. Storing the user-entered pattern (with whatever "blank" char they chose to use) see issue Browsing back/forward in browser history doesn't reload the results #15.

Links to read up on:

• Safari Developer Library: Client-Side Storage and Offline Applications Programming Guide
• Dive into HTML5: Local Storage