The Hue API returns a "capabilities" key along with each light that
specifies the parameters available for the light. These capabilities
allow subsequent requests/settings to be made more intelligently
depending on the features supported by the luminaire.

Removed redundant light.On calls from README example

Correct some Action fields to be pointers

Since we specify omitempty on all Action fields it's important that
fields whose empty values are valid values to marshal, we must use
pointer types, so that the empty value is nil, not the empty value of
the type

For example, prior to this change you could not specify On: false and
have it correctly be marshaled into a Action JSON.