* Tulip issue #183: log socket events in debug mode

  - Log most important socket events: socket connected, new client, connection
    reset or closed by peer (EOF), etc.
  - Log time elapsed in DNS resolution (getaddrinfo)
  - Log pause/resume reading
  - Log time of SSL handshake
  - Log SSL handshake errors
  - Add a __repr__() method to many classes

* Fix ProactorEventLoop() in debug mode. ProactorEventLoop._make_self_pipe()
  doesn't call call_soon() directly because it checks for the current loop
  which fails, because the method is called to build the event loop.

* Cleanup _ProactorReadPipeTransport constructor. Not need to set again
  _read_fut attribute to None, it is already done in the base class.