* Add: Py-Plotly
The requirements of py-plotlit are rather strict fixed to specific
versions, so I did not add an "upper versions" `:` to the constrains.
See
https://github.com/plotly/plotly.py/blob/master/requirements.txt
* Py-Requests, Py-Six, Py-Pytz: Older Versions
Add two older versions of requests, pytz and six for plotly.
