Prepare v0.12.0b6 release

Author: kbattocchi

README.md

@@ -45,10 +45,12 @@ For information on use cases and background material on causal inference and het
 
 # News
 
-**August 3, 2021:** Release v0.12.0b5, see release notes [here](https://github.com/Microsoft/EconML/releases/tag/v0.12.0b5)
+**August 5, 2021:** Release v0.12.0b6, see release notes [here](https://github.com/Microsoft/EconML/releases/tag/v0.12.0b6)
 
 <details><summary>Previous releases</summary>
 
+**August 3, 2021:** Release v0.12.0b5, see release notes [here](https://github.com/Microsoft/EconML/releases/tag/v0.12.0b5)
+
 **July 9, 2021:** Release v0.12.0b4, see release notes [here](https://github.com/Microsoft/EconML/releases/tag/v0.12.0b4)
 
 **June 25, 2021:** Release v0.12.0b3, see release notes [here](https://github.com/Microsoft/EconML/releases/tag/v0.12.0b3)

econml/_version.py

@@ -1,4 +1,4 @@
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License.
 
-__version__ = '0.12.0b5'
+__version__ = '0.12.0b6'