added param to make lollipop scale with carbs

@jebeck or @nicolashery Small change to make add param to make lollipop scale with carbs
I'd be ok with either. As you said @jebeck, letting a "controller" component like `PatientData` access query parameters value directly means we can add more query parameters later without touching the rest of the app. And as @cheddar suggest, building a `config` prop earlier hides the fact that it comes from query parameters, so we could make it come from something else (like general user settings), without affecting `PatientData`. To early to tell which is more useful I guess.