Fix typo in CONTRIBUTING.md

Author: devonharvey

CONTRIBUTING.md

@@ -10,6 +10,6 @@ Please follow these pull request guidelines:
 
 5. New features should be covered by accompanying QUnit tests.
 
-6. Keep your commits as atomar as possible, i.e. create a new commit for every single bug fix or feature added.
+6. Keep your commits as atomic as possible, i.e. create a new commit for every single bug fix or feature added.
 
 7. Always add meaningful commit messages.