"whereami" needs to take into account timing

Repeatedly issuing "whereami" within some small period of time should walk up the tree. That is not currently implemented. The idea is that the first time someone asks "whereami" it says "a+b" inside "fraction a+b over 2". If you ask again, it should walk all the way up the tree saying where it is.

This should be based on an estimate of how long it takes to speak the command along some delay (10 seconds?). The delay should probably be a user preference.