Currently forcesell only cancels an open limit buy order and doesn't sell the filled amount.
After this change, forcesell will also update trade's amount to filled amount and sell the filled amount.
* remove obsolete helper functions and make _state a public member.
* remove function assertions
* revert worker() changes
* Update pytest from 3.4.2 to 3.5.0
* Adapt exchange functions to ccxt API
Remove get_market_summaries and get_wallet_health, add exception handling
* Add NetworkException
* Change pair format in constants.py
* Add tests for exchange functions that comply with ccxt
* Remove bittrex tests
* Remove Bittrex and Interface classes
* Add retrier decorator
* Remove cache from get_ticker
* Remove unused and duplicate imports
* Add keyword arguments for get_fee
* Implement 'get_pair_detail_url'
* Change get_ticker_history format to ccxt format
* Fix exchange urls dict, don't need to initialize exchanges
* Add "Using Exchange ..." logging line
