Modify ReadBuffer for Py3

On my Python 3.4.2 environment, UserStreaming did't work
because of an error of bytes-to-str conversion.

And also my Python 2.7.8 environment, UserStreaming didn't work
because of UnicodeDecodeError.
To solve this problem, I added following to my code which imports tweepy.

  import sys
  reload(sys)
  sys.setdefaultencoding('UTF-8')