text: Title: Client doesn't work on simple example. Error: simplejson.errors.JSONDecodeError
  Body: I'm trying to run the simple example:
  ```
  import socketio
  
  sio = socketio.Client()
  
  @sio.event
  def connect():
      print('connected to server')
  
  @sio.event
  def disconnect():
      print('disconnected from server')
  
  sio.connect('wss://echo.websocket.org')
  sio.wait()
  ```
  
  but I'm getting an error:
  `Traceback (most recent call last):
    File "cli.py", line 15, in <module>
      sio.connect('wss://echo.websocket.org')
    File "/home/ihor/.local/lib/python3.6/site-packages/socketio/client.py", line 275, in connect
      engineio_path=socketio_path)
    File "/home/ihor/.local/lib/python3.6/site-packages/engineio/client.py", line 187, in connect
      url, headers or {}, engineio_path)
    File "/home/ihor/.local/lib/python3.6/site-packages/engineio/client.py", line 292, in _connect_polling
      arg = r.json()
    File "/home/ihor/.local/lib/python3.6/site-packages/requests/models.py", line 900, in json
      return complexjson.loads(self.text, **kwargs)
    File "/usr/lib/python3/dist-packages/simplejson/__init__.py", line 518, in loads
      return _default_decoder.decode(s)
    File "/usr/lib/python3/dist-packages/simplejson/decoder.py", line 370, in decode
      obj, end = self.raw_decode(s)
    File "/usr/lib/python3/dist-packages/simplejson/decoder.py", line 400, in raw_decode
      return self.scan_once(s, idx=_w(s, idx).end())
  simplejson.errors.JSONDecodeError: Expecting value: line 1 column 1 (char 0)`
  
  I tried also to import json module and set it to sio.Client(json=json) but got the same error. Please advice the solution.