pypubsub update

[Oliver]

I have finally completed pypubsub update after 2 years: migration the code to be hosted on github, updating tox, setting up travis CI and readthedocs (all the while preserving the docs for pypubsub 3.3), updating setup.py, and simplifying version management.

Other important code changes:

• Support Python 3.5 and 3.6
  
• Use PEP 484 style of annotations throughout: abandon support for Python 2.x
  
• Abandon support for (long-ago deprecated) arg1 messaging protocol (simplified code base considerably)
  
• Added currying of subscribed listener args
  
• Significant speed improvement for message delivery (can be factor of 2 or even more depending on details of your topic tree and message argumnets)
  
• Updating the docs, all the doc links, the build bot links etc after arg1 dropped, wheel-based installation, etc
  

If you could try "pip install --pre pypubsub" and post any issues you encounter, that would be much appreciated.
Oliver