react.js doesn't recognize camel case data-* attrs

sablono transforms data-* attrs to camel case, and they then get ignored by react and are absent from the DOM

this patch treats data-* attrs specially, and does not transform them to camel case : data-* attributes are now present in the resulting DOM

i haven't tested it, but it may be that aria-* attributes require similar treatment ( since they are lumped together with data-* attributes here : http://facebook.github.io/react/docs/tags-and-attributes.html )