Update release table (#4221)

Author: awjuliani

README.md

@@ -48,7 +48,7 @@ descriptions of all these features.
 
 ## Releases & Documentation
 
-**Our latest, stable release is `Release 3`. Click
+**Our latest, stable release is `Release 4`. Click
 [here](https://github.com/Unity-Technologies/ml-agents/tree/release_4_docs/docs/Readme.md)
 to get started with the latest release of ML-Agents.**
 
@@ -67,15 +67,14 @@ under active development and may be unstable. A few helpful guidelines:
 | **Version** | **Release Date** | **Source** | **Documentation** | **Download** |
 |:-------:|:------:|:-------------:|:-------:|:------------:|
 | **master (unstable)** | -- | [source](https://github.com/Unity-Technologies/ml-agents/tree/master) | [docs](https://github.com/Unity-Technologies/ml-agents/tree/master/docs/Readme.md) | [download](https://github.com/Unity-Technologies/ml-agents/archive/master.zip) |
-| **Release 3** | **June 10, 2020** | **[source](https://github.com/Unity-Technologies/ml-agents/tree/release_4)** | **[docs](https://github.com/Unity-Technologies/ml-agents/tree/release_4_docs/docs/Readme.md)** | **[download](https://github.com/Unity-Technologies/ml-agents/archive/release_4.zip)** |
+| **Release 4** | **July 15, 2020** | **[source](https://github.com/Unity-Technologies/ml-agents/tree/release_4)** | **[docs](https://github.com/Unity-Technologies/ml-agents/tree/release_4_docs/docs/Readme.md)** | **[download](https://github.com/Unity-Technologies/ml-agents/archive/release_4.zip)** |
+| **Release 3** | June 10, 2020 | [source](https://github.com/Unity-Technologies/ml-agents/tree/release_3) | [docs](https://github.com/Unity-Technologies/ml-agents/tree/release_3_docs/docs/Readme.md) | [download](https://github.com/Unity-Technologies/ml-agents/archive/release_3.zip) |
 | **Release 2** | May 20, 2020 | [source](https://github.com/Unity-Technologies/ml-agents/tree/release_2) | [docs](https://github.com/Unity-Technologies/ml-agents/tree/release_2_docs/docs/Readme.md) | [download](https://github.com/Unity-Technologies/ml-agents/archive/release_2.zip) |
 | **Release 1** | April 30, 2020 | [source](https://github.com/Unity-Technologies/ml-agents/tree/release_1) | [docs](https://github.com/Unity-Technologies/ml-agents/tree/release_1_docs/docs/Readme.md) | [download](https://github.com/Unity-Technologies/ml-agents/archive/release_1.zip) |
 | **0.15.1** | March 30, 2020 | [source](https://github.com/Unity-Technologies/ml-agents/tree/0.15.1) | [docs](https://github.com/Unity-Technologies/ml-agents/tree/0.15.1/docs/Readme.md) | [download](https://github.com/Unity-Technologies/ml-agents/archive/0.15.1.zip) |
 | **0.15.0** | March 18, 2020 | [source](https://github.com/Unity-Technologies/ml-agents/tree/0.15.0) | [docs](https://github.com/Unity-Technologies/ml-agents/tree/0.15.0/docs/Readme.md) | [download](https://github.com/Unity-Technologies/ml-agents/archive/0.15.0.zip) |
 | **0.14.1** | February 26, 2020 | [source](https://github.com/Unity-Technologies/ml-agents/tree/0.14.1) | [docs](https://github.com/Unity-Technologies/ml-agents/tree/0.14.1/docs/Readme.md) | [download](https://github.com/Unity-Technologies/ml-agents/archive/0.14.1.zip) |
-| **0.14.0** | February 13, 2020 | [source](https://github.com/Unity-Technologies/ml-agents/tree/0.14.0) | [docs](https://github.com/Unity-Technologies/ml-agents/tree/0.14.0/docs/Readme.md) | [download](https://github.com/Unity-Technologies/ml-agents/archive/0.14.0.zip) |
-| **0.13.1** | January 21, 2020 | [source](https://github.com/Unity-Technologies/ml-agents/tree/0.13.1) | [docs](https://github.com/Unity-Technologies/ml-agents/tree/0.13.1/docs/Readme.md) | [download](https://github.com/Unity-Technologies/ml-agents/archive/0.13.1.zip) |
-| **0.13.0** | January 8, 2020 | [source](https://github.com/Unity-Technologies/ml-agents/tree/0.13.0) | [docs](https://github.com/Unity-Technologies/ml-agents/tree/0.13.0/docs/Readme.md) | [download](https://github.com/Unity-Technologies/ml-agents/archive/0.13.0.zip) |
+
 ## Citation
 
 If you are a researcher interested in a discussion of Unity as an AI platform,