pre-v0.8 refactoring

[justheuristic]

A list of small issues to be solved in bulk before we bump the version

Clean up utils:

• Remove Connection after we switch to grpc-based connections ( Asyncio connection handlers + logging #45 )
• Do we really need this many serializers? (or serializers.py at all)
• relative vs absolute imports: discuss
• SharedFuture:
  • decided to update and keep it
  • rename to MPFuture?
• utils.data - maybe rename or merge into utils/__init__.py?
• Check if concurrent autograd is still necessary in pytorch 1.5 (maybe bump version)
  • no, but we only need it for _RemoteModuleCall.backward
    • Lets implement custom code in moe.py and ditch autograd.py!
• (delayed) remove find_open_port in favor of builtin port picker or reserve_port (reason: find_open_port fails ~1-3% of the time)

Discussion: gRPC proto files

• switch from compile_grpc function to pre-compiling in setup.py? (if so: add to pb2 files to .gitignore)
• use a dedicated folder to store .proto files

Etc:

• maybe merge hivemind.runtime back into hivemind.server?
• move all "Thanks to X" notes to acknowledgements section in the readme
• update PyPI package (0.8.0)
• create a test case for python -m test_utils.run_server (rationale: we broke it on more than one occasion)
• msgpackserializer - use strict type checking
• allow setting max_send/receive_message_length when creating a server
• conn_handler_processes => num_connection_handlers to avoid confusion?
• which branches do we still need?