docs: update changelog

CHANGELOG.md

+<a name="0.3.1"></a>
+## 0.3.1 (2021-04-14)
+
+Just a quick release because I broke docs.rs :)
+
+#### Bug Fixes
+
+* **build:**  remove .cargo/config.toml to make docs.rs happy ([393d9807](https://github.com/zkat/big-brain/commit/393d9807576d21c7234667b1f9914f1886579bd0))
+
+
 <a name="0.3.0"></a>
 ## 0.3.0 (2021-04-14)
 
@@ -20,5 +30,3 @@ Probably.
 * New builder-based Thinker API!
 * Composite Scorers: `FixedScore`, `AllOrNothing`, and `SumOfScorers`.
 * Composite Action: `Steps`, for sequential Action execution.
-
-