Changing value via [colorPicker] should not cause a (colorPickerChange) event to fire.

[ImAllInNow]

We are attempting to use this color picker to choose the color of a ui element in our system. We have an undo/redo system to allow users to undo changes they make. We listen for (colorPickerChange) to add items to our undo/redo stack. When a change is undone, the color of the ui element changes which is passed to the color picker via [colorPicker]. But this in turn causes another (colorPickerChange) event to fire. This results in committing a new item to the stack when there shouldn't be one.

similar to this issue with md-checkbox: angular/components#820