Warnings check is performed by RuboCop

Author: sferik

CONTRIBUTING.md

@@ -38,13 +38,11 @@ Ideally, a bug report should include a pull request with failing specs.
 6. Run `bundle exec rake`. If your specs fail, return to step 5.
 7. Run `open coverage/index.html`. If your changes are not completely covered
    by your tests, return to step 3.
-8. Run `RUBYOPT=W2 bundle exec rake spec 2>&1 | grep twitter`. If your changes
-   produce any warnings, return to step 5.
-9. Add documentation for your feature or bug fix.
-10. Run `bundle exec rake verify_measurements`. If your changes are not 100% documented, go
-    back to step 9.
-11. Commit and push your changes.
-12. [Submit a pull request.][pr]
+8. Add documentation for your feature or bug fix.
+9. Run `bundle exec rake verify_measurements`. If your changes are not 100%
+   documented, go back to step 8.
+10. Commit and push your changes.
+11. [Submit a pull request.][pr]
 
 [fork]: http://help.github.com/fork-a-repo/
 [branch]: http://learn.github.com/p/branching.html