TabError: inconsistent use of tabs and spaces in indentation in test_strategy_backtest.py

[femtotrader]

There is an issue with test_strategy_backtest.py

It raises TabError: inconsistent use of tabs and spaces in indentation in test_strategy_backtest.py
see https://raw.githubusercontent.com/mhallsmoore/qstrader/master/examples/test_strategy_backtest.py

    # Use the TestCompliance component
    compliance = TestCompliance();

    # Use a simulated IB Execution Handler
    execution_handler = IBSimulatedExecutionHandler(
        events_queue, price_handler, compliance
    )

[femtotrader]

In addition to unit tests, runing in Travis random price generation and sample strategies will help to catch this kind of issue

see mhallsmoore/qsforex#19

[femtotrader]

Closed by #48