githubsearch: remove cookie serialization of saved searches, set html "title" element for bookmarks instead

[rmuir]

The saved searches are a bit wonky as they are serialized in cookie and will overflow cookie maximums quickly.

Instead, just suggest the user use bookmarks (e.g. hit ^D) to save searches? they already work, just aren't very usable because <title> isn't being set. If you search on "OOME", maybe we should just set <title>githubsearch: OOME</title> so that it has a nice "name" in your bookmarks when you add it.

[mikemccand]

Also, the cookies do not survive browser restart ;) They are apparently merely "session cookies" now!