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/peerinfo.py

@@ -1,5 +1,42 @@
+import multiaddr
+import multiaddr.util
+from peer.id import id_b58_decode
+from peer.peerdata import PeerData
+
+
 class PeerInfo:
 	# pylint: disable=too-few-public-methods
     def __init__(self, peer_id, peer_data):
         self.peer_id = peer_id
         self.addrs = peer_data.get_addrs()
+
+
+def info_from_p2p_addr(addr):
+    if not addr:
+        raise InvalidAddrError()
+
+    parts = multiaddr.util.split(addr)
+    if not parts:
+        raise InvalidAddrError()
+
+    ipfspart = parts[-1]
+    if ipfspart.protocols()[0].code != multiaddr.protocols.P_IPFS:
+        raise InvalidAddrError()
+
+    # make sure the /ipfs value parses as a peer.ID
+    peer_id_str = ipfspart.value_for_protocol(multiaddr.protocols.P_IPFS)
+    peer_id = id_b58_decode(peer_id_str)
+
+    # we might have received just an / ipfs part, which means there's no addr.
+    if len(parts) > 1:
+        addr = multiaddr.util.join(parts[:-1])
+
+    peer_data = PeerData()
+    peer_data.addrs = [addr]
+    peer_data.protocols = [p.code for p in addr.protocols()]
+
+    return PeerInfo(peer_id, peer_data)
+
+
+class InvalidAddrError(ValueError):
+    pass