IG Integration and logging feature

[dsdinter]

Hi,
Just wanted to share my own implementation to integrate Qstrader with IG, https://www.ig.com and logging feature.
This PR includes:
Logging feature which can be used in other parts of Qstrader
Portfolio handler abstracted to include new implementations, e.g., IG
Integration with IG using library https://github.com/ig-python/ig-markets-api-python-library
It also includes some test coverage but nothing mockup so there is plenty of room for improvement
The below parameters are now required to connect with your IG account (Required for tests also):
IG_USERNAME
IG_PASSWORD
IG_API_KEY
IG_ACC_TYPE
IG_ACC_ID

Let me know your views, please.

Thanks.

[dsdinter]

Travis failed due to missing env variables:
"IG_USERNAME"
"IG_PASSWORD"
"IG_API_KEY"
"IG_ACC_TYPE"
"IG_ACC_ID"
It also fails as we need to refactor the new portfolio_handler module, what do you think is the best approach here?

1. Refactor new portfolio_handler (This is what I did in my private repo, just need to add the generic_handler and generic_portfolio in module and refactor)
2. Create separate portfolio_handler for IG in root folder

[dsdinter]

Travis also fails while trying to import module request.
It comes from trading_ig, this module is not supporting Python 2.7 currently (It leverages urllib.request module which only exists in Python 3.
https://stackoverflow.com/questions/41431780/python-2-7-cannot-find-module-request-from-urllib-request