Initial work on a Kademlia implementation for Python 3 asyncio.

Implemented a simple RPC-over-UDP system as the basis for the Kademlia
protocol, the heart of which are the 4 RPCs `ping`, `store`, `find_node`,
and `find_value`.  A naive implemenation of `ping`, `store` as well as
the naive shortcut case of `find_value` are included in this.

Note that with this commit, we've got the basic plumbing for RPCs, but
none of the important hashtable implementation.

Also, setup.py and README.md are empty ;)
The seed of a Kademlia routing table, with some tests.  Also, a bit of Python packaging in order to use tox.
Adding some words to the README.md
A test and implementation for `RoutingTable.find_closest_peers`.
Tests for the routing table and basic RPC tests.
Implementations of the find_node and find_value RPCs.
Building a rough verison of the core iterative `lookup_node` procedure, which
appears to be somewhat working.  As of this version, I can store values in the
network (manually with the direct RPC calls), use `lookup_node` to find the
closest node to a key, then use RPC to retrieve that value.

Conceivably, the iterative `put` and `get` will be trivial to implement on
top of this.

Refactored some common operational things into the main package, and changed
`__main__` to always run a single standalone server, added `local_network.py`
as a self-contained 10-node network, and `local_client.py` which starts a node
and launches an embedded IPython for interactive testing.

Note, the `local_client.py` script does *not* (yet) join the local_network, as
this is part of what I'm still trying to build.
Refining the `KademliaNode.lookup_node` routine to be simpler and to
return the `k` closest nodes rather than attempting to track the
closest.  Alos implementing the iterative `put` routine.