hashpipe.js: add control popup.

The control popup has show/hide toggle and next prev buttons which
iterate through the list of existing anchor tags.

Also, clean up some stuff in index.html and use the new HashPipe
module to go previous and next anchor using left and right arrow keys.
Bookmarklet progress. Move external code into HashPipe object.
Connect using control popup instead of automatically.
Show connect/disconnect.
Add server message events.