Prepare v0.12.0b3 release

Author: kbattocchi

README.md

@@ -45,10 +45,12 @@ For information on use cases and background material on causal inference and het
 
 # News
 
-**June 18, 2021:** Release v0.12.0b2, see release notes [here](https://github.com/Microsoft/EconML/releases/tag/v0.12.0b2)
+**June 25, 2021:** Release v0.12.0b3, see release notes [here](https://github.com/Microsoft/EconML/releases/tag/v0.12.0b3)
 
 <details><summary>Previous releases</summary>
 
+**June 18, 2021:** Release v0.12.0b2, see release notes [here](https://github.com/Microsoft/EconML/releases/tag/v0.12.0b2)
+
 **June 7, 2021:** Release v0.12.0b1, see release notes [here](https://github.com/Microsoft/EconML/releases/tag/v0.12.0b1)
 
 **May 18, 2021:** Release v0.11.1, see release notes [here](https://github.com/Microsoft/EconML/releases/tag/v0.11.1)

econml/__init__.py

@@ -26,4 +26,4 @@
            'dowhy',
            '__version__']
 
-__version__ = '0.12.0b2'
+__version__ = '0.12.0b3'