reader: python3 type error in nsqlookupd response parsing

[mikolajb]

Tornado's HTTPResponse body is of type bytes in Python3 and json.loads cannot be performed.

Execution of:

import tornado.ioloop
import nsq


def handler(message):
    print(message)
    return True

r = nsq.Reader(message_handler=handler,
               lookupd_http_addresses=['nsqlookupd:4161'],
               topic='test', channel='test', lookupd_poll_interval=15)
nsq.run()

tornado.ioloop.IOLoop.current().start()

Results with:

Traceback (most recent call last):
  File "/usr/local/lib/python3.5/site-packages/tornado/ioloop.py", line 604, in _run_callback
    ret = callback()
  File "/usr/local/lib/python3.5/site-packages/tornado/stack_context.py", line 275, in null_wrapper
    return fn(*args, **kwargs)
  File "/usr/local/lib/python3.5/site-packages/nsq/reader.py", line 597, in _finish_query_lookupd
    lookup_data = json.loads(response.body)
  File "/usr/local/lib/python3.5/json/__init__.py", line 312, in loads
    s.__class__.__name__))
TypeError: the JSON object must be str, not 'bytes'

Clarification of what is a type of HTTPResponse.body:
tornadoweb/tornado@d1cab4a

[mreiferson]

Thanks!