Protocol muxing (#82)

* Implement protocol muxing

* Integrate protocol muxing into new stream and listen's conn handler

* Fix bugs in protocol muxing

* Remove blank line

* Add comments and fix linting issues

* Fix order of parameters to select_one_of to match interface

* Use array of protocol ids in new stream instead of protocol id

* Add basic protocol muxer tests

* Add todo

* Modify new stream to take in protocol ids

* Add check to all tests to ensure protocol id is saved to net stream properly

* Lint tests

* Fix lint issues

* Add todo

* Modify port numbers in tests

* Fix linting issues

* Add more documentation to functions

* Add docs describing classes and fix indent error

protocol_muxer/multiselect_client_interface.py

@@ -0,0 +1,28 @@
+from abc import ABC, abstractmethod
+
+class IMultiselectClient(ABC):
+    """
+    Client for communicating with receiver's multiselect
+    module in order to select a protocol id to communicate over
+    """
+
+    @abstractmethod
+    def select_protocol_or_fail(self, protocol, stream):
+        """
+        Send message to multiselect selecting protocol
+        and fail if multiselect does not return same protocol
+        :param protocol: protocol to select
+        :param stream: stream to communicate with multiselect over
+        :return: selected protocol
+        """
+
+    @abstractmethod
+    def select_one_of(self, protocols, stream):
+        """
+        For each protocol, send message to multiselect selecting protocol
+        and fail if multiselect does not return same protocol. Returns first
+        protocol that multiselect agrees on (i.e. that multiselect selects)
+        :param protocol: protocol to select
+        :param stream: stream to communicate with multiselect over
+        :return: selected protocol
+        """