Bump version to 0.9.0

Author: kbattocchi

README.md

@@ -45,10 +45,12 @@ For information on use cases and background material on causal inference and het
 
 # News
 
-**January 20, 2021:** Release v0.9.0b1, see release notes [here](https://github.com/Microsoft/EconML/releases/tag/v0.9.0b1)
+**February 20, 2021:** Release v0.9.0, see release notes [here](https://github.com/Microsoft/EconML/releases/tag/v0.9.0)
 
 <details><summary>Previous releases</summary>
 
+**January 20, 2021:** Release v0.9.0b1, see release notes [here](https://github.com/Microsoft/EconML/releases/tag/v0.9.0b1)
+
 **November 20, 2020:** Release v0.8.1, see release notes [here](https://github.com/Microsoft/EconML/releases/tag/v0.8.1)
 
 **November 18, 2020:** Release v0.8.0, see release notes [here](https://github.com/Microsoft/EconML/releases/tag/v0.8.0)

econml/__init__.py

@@ -9,4 +9,4 @@
            'score', 'sklearn_extensions', 'tree',
            'two_stage_least_squares', 'utilities', "dowhy", "__version__"]
 
-__version__ = '0.9.0b1'
+__version__ = '0.9.0'