Tradingstrategy

- Correct RSI_EMA, RSI_SMA subclassing
- Add cheat-on-close to the broker
- Correct own operation bug directly on lines (was fine on line
actions/operations)
- Add support for __neg__ operator (-) to lines
- Adresses 170 by forcing a bool as return
- Extend signal trigger detection to inverse and any values
- Support for embedding in a line non-line types
- Closes 171. Make safepow the default
- Use DataTrades only if several datas are in place

- Workaround IbPy not converting bytes by passing strings in Python3
- safepow parameter for StandardDeviation

- Closes 156 by adding LinePlotterIndicator
- Closes 154 by providing hollow candlesticks
- Ensure unique name for analyzers to get all printed out by writers
- Fix installation instructions for plotting

- Allow defining the datetime format string for the x axis and data points.
Closes 148
- Rework plotting to account for datas with different lengths and work with
auto locators/formatters
- Improve signals to handle multiple datas and wrap LineIterators (Indicators)
- Use excess returns for the standard deviation in Sharpe Ratio

- Improve data synchronization behavior
- Make new DataTrades synchronize to strategy
- Correct TimeFrameAnalyzerBase to synchronize with strategy

- Add DataTrades Observer to plot the trades of multiple datas independently
- Make this observer the default in cerebro (old behavior via oldtrades=True)