Fix for bug #950472

1. Change to use the correct data field - was "text", changed to "content"
2. Strip all markup tags before applying regex matching
3. Rewrite search form submit handler to register with event "submit" and
surpress event propagation
4. Add calls to hide search title and clear search box when a notebook is
opened after a search
Merge pull request #3 from yor-mozilla-com/fix950472

Fix for bug #950472