Adjust the default robots.txt

The new rules say:

Don't index anything in and below /bags and /recipes

This means that what google will index is the "friendly" stuff
that is found at /: / itself, /tiddlers and /<friendly_uris>.

This is a precursor to fixing the html on tiddlyspace. See:

   http://cdent.tiddlyspace.com/Fixing%20TiddlySpace%20HTML