Issue #868. Add note to explain how to run imagemin.

Mike Taylor · Mike Taylor · commit 0b4b599a4af3 · 2015-12-21T19:24:22.000-06:00
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
@@ -362,6 +362,7 @@ grunt
  make watch
  ```
 
+By default, a build will *not* optimize images (which is done before deploys). If you'd like to do that, you can run `grunt imagemin`.
 
 ## Running Tests
 
