Fix typo

Author: jakezatecky

CHANGELOG.md

@@ -18,7 +18,7 @@
 ### Bug Fixes
 
 * [#89]: Fix misnamed variables in the Less stylesheets
-* [#90]: Coerce NaN types to string when outputing DOM IDs
+* [#90]: Coerce NaN types to string when outputting DOM IDs
 
 ## [v1.2.1](https://github.com/jakezatecky/react-checkbox-tree/compare/v1.2.0...v1.2.1) (2018-05-10)