Assignment of the --paper-input-container-color variable is wrong

I think that you intended to assign `--paper-input-container-color` to `--disabled-on-card-dialog-color`, rather than to `--disabled-text-on-card-dialog-color` (which does not exist).

See here: https://github.com/David-Mulder/paper-theme/blob/master/standard-styles.html#L4

I can submit a PR if you want.
