Notify user when a search request is pending in the background.

If a request takes a long time then there was no indication that
something was still going on in the background or that the currently
displayed results do not match the contents of the search box.
Merge branch 'master' of github.com:abbeyj/dxr into search-status

Conflicts:
	dxr/static/search.js
Notification when there is a search in progress.
Now with less flicker.
Merge branch 'master' of github.com:abbeyj/dxr into search-status
Standardize on lowerCamelCase. Reformat some code.
Eliminate flicker in "search in progress" indicator. Fix #126.