Fixes data-colors bug in HTML5 configuration

Before the fix, to set the plate color (plate is used as exemple, any
        data-color property would fail), it was necessary to declare

    data-color-XXX-plate = '#aaa'

After the fix:

    data-color-plate = '#aaa'

As the docs suggest.
Merge pull request #8 from invernizzi/master

data-colors fix