docs: Update CONTRIBUTING.md

Fixes #241

Author: holtskinner

CONTRIBUTING.md

@@ -4,20 +4,6 @@ We'd love to accept your patches and contributions to this project.
 
 ## Before you begin
 
-### Sign our Contributor License Agreement
-
-Contributions to this project must be accompanied by a
-[Contributor License Agreement](https://cla.developers.google.com/about) (CLA).
-You (or your employer) retain the copyright to your contribution; this simply
-gives us permission to use and redistribute your contributions as part of the
-project.
-
-If you or your current employer have already signed the Google CLA (even if it
-was for a different project), you probably don't need to do it again.
-
-Visit <https://cla.developers.google.com/> to see your current agreements or to
-sign a new one.
-
 ### Review our community guidelines
 
 This project follows