add not upgraded hint
add not upgraded hint

google/playground-elements,PolymerLabs/playground-elements,PolymerLabs/playground-elements,PolymerLabs/code-sample-editor-package,PolymerLabs/code-sample-editor-package,PolymerLabs/code-sample-editor-package,PolymerLabs/playground-elements,PolymerLabs/code-sample-editor,google/playground-elements,PolymerLabs/code-sample-editor,PolymerLabs/code-sample-editor,google/playground-elements