import modules into constructor registry, rather than the other way
around.  then constructors have to be declared in factory.py, which
isn't optimal but makes dependencies nicer in node.py.  how this gets
done should probably be rethought.
add *args to init
added a TODO file to keep track of ideas/issues as we go.
add some musings
threaded Nodes will be necessary one day
add some TODOs about the current state of endpoints and error handling.
add a clause for when a user requests a SET.  this actually does work,
amazingly.
dripline_agent todos
now dripline agent can set values too.
raise a ValueError if the set value cannot be represented as a float.
initial value key is now supported completely
more dripline_agent griping
a note about authentication
more on endpoint abstraction
cache the result of reading lines from the yaml config file.
try to catch problem connecting to broker and log it.
note about Config's in-memory representation
add a send_sync to Node for sending requests across the mesh
synchronously.
use the new Node.send_sync interface instead of raw calls to the
connection which is owned by the Node instance
documentation TODO