first steps toward saving tree state.  added tree_state to model, added failing test
made sure capitalization of commands is limited to appropriate areas.
introducing the concept of processor modules, which can be chained.  Presently only command and tree modules.
additional logic added to message tree processing.  test still failing
added functionality for using tree from message line
case where user is not subscribed to a tree
added more tests: not subscribed to anything, and two successive tree requests