cleanup instance per test file
When a tiddler does not exist, give a list of sisters

At the moment this only works when the other tiddlers are in
tanks that have no spaces in the names. This is due to a limitation
in the markdown plugin

   tiddlyweb/tiddlywebplugins.markdown#24

This is being created to encourage inter-tank transclusion.
Merge branch 'master' of github.com:cdent/tank