Add basic support for multiaddr addresses and improvement around peer id (#75)

* Improved peer ID construction and usage

* peer id object is directly passed to the network

no need to cast from a string to an ID

* don't base64 encode the peer id when loading from public key

* use proper multiaddr address

- keep multiaddr object into peerstore instead of string
- update network code to use new multiaddr lib
- update tests and example

* don't instanciate peerstore object in constructor

This has side effect where the same peerstore
is used for different instance of Libp2p

* add connect method to basic_host

* use zaibon's fork of sbuss/py-multiaddr

* lint

peer/peerstore.py

@@ -42,7 +42,7 @@ class PeerStore(IPeerStore):
         peer.set_protocols(protocols)
 
     def peers(self):
-        return self.peer_map.keys()
+        return list(self.peer_map.keys())
 
     def get(self, peer_id, key):
         if peer_id in self.peer_map: