Stock-indicators

New indicators:

- Double Exponential Moving Average (DEMA)
- ConnorsRSI

Chores:

- protected SET on Index property in Quote and various results classes.

If you are using derived classes for any of these, see the [using derived classes](https://daveskender.github.io/Stock.Indicators/GUIDE.html#using-derived-classes) section in the Guide for more information.

The 7th release of **Stock Indicators for Python**, a Python wrapper of the Stock Indicators for .NET library.

> Please treat all versions before 1.0.0 as previews. **Expect breaking changes as we get more [community feedback](https://github.com/DaveSkender/Stock.Indicators.Python/issues) and fine-tune everything.** We will enumerate breaking changes in these release notes.

Our priorities going forward are to:

1. add all of the indicators from [Stock Indicators for .NET](https://daveskender.github.io/Stock.Indicators/).
2. work on performance tuning to improve library speed

**New Indicators**
- Gator Oscillator
- Moving Average Envelopes
- Percentage Volume Oscillator
- Pivot Points
- Pivots
- Renko Chart
- Rolling Pivot Points

**Updated Indicators**
- Beta Coefficient
- Chandelier Exit
- Williams Alligator

**Dependency**
- Bump pythonnet from 2.5.2 to 3.0.0a1
- Use .NET Standard 2.1 instead of .NET Standard 2.0.


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For more information, see the:

- [documentation site](https://daveskender.github.io/Stock.Indicators.Python/)
- [PyPI project page](https://pypi.org/project/stock-indicators/)

**Full Changelog**: https://github.com/DaveSkender/Stock.Indicators.Python/compare/0.6.0...0.7.0+24

New indicators:

- Keltner Channel
- Donchain Channel
- William %R
- R-Squared added to Correlation Coefficient output

Chores:

- update Chaikin Oscillator history requirements
- add unit tests for better code coverage

New indicators:

- On-balance Volume (OBV)
- Accumulation Distribution Line (ADL)
- Chaikin Money Flow (CMF)
- Chaikin Oscillator
- Rate of Change (ROC)

Chores:

- cleanup naming conventions
- update documentation

Updated SMA indicator with additional result elements: 45

- Mean Absolute Deviation
- Mean Square Error
- Mean Absolute Percentage Error

Updated indicators:

- Added more appropriate validation on EMA history requirements. Please note that this indicator does require substantially more history due to convergence. For example, an EMA(250) requires more than 3 years of history.
Given that you may be getting your history from a feed, you'll need to handle the `BadHistoryException` or pre-validate the history you're getting to avoid surprises and errors.

- Reverted nullability for IsBullish flag on Heikin-Ashi. It was an unnecessary change.

Chores:

- Added Index value to test data spreadsheet