Client.py line 1230 -- stream_bars_back

[eyesuk]

Hello Mr Reed As always thank you very much for your work on these APIs they are nothing short of awesome.
While trying to obtain historical data using stream_bars_back I received a datetime error. Error: 'datetime.datetime' has no attribute 'datetime'

After some troubleshooting I changed the following lines and it fixed the issue:

Line 16 from datetime import datetime was changed to: import datetime

Line 1230 url='stream/barchart/{symbol}/{interval}/{unit}/{bar_back}/{last_date}' was changed to: url='stream/barchart/{symbol}/{interval}/{unit}/{bar_back}/{last_date_iso}'

Seems like this fix also fixed others stream_bars_* functions

[akopdev]

@eyesuk here is PR for that https://github.com/areed1192/tradestation-python-api/pull/10