MNT: Update CHANGELOG for 0.3.0

Author: kernc

CHANGELOG.md

@@ -6,6 +6,10 @@ These were the major changes contributing to each release:
 
 ### 0.x.x
 
+
+### 0.3.0
+(2020-11-24)
+
 * Faster [model-based optimization](https://kernc.github.io/backtesting.py/doc/examples/Parameter%20Heatmap%20&%20Optimization.html#Model-based%20optimization) using scikit-optimize (#154)
 * Optionally faster [optimization](https://kernc.github.io/backtesting.py/doc/backtesting/backtesting.html#backtesting.backtesting.Backtest.optimize) by randomized grid search (#154)
 * _Annualized_ Return/Volatility/Sharpe/Sortino/Calmar stats (#156)