refactor(StickyCell): convert findDOMNode calls (#923)
refactor(StickyCell): convert findDOMNode calls (#923)

Closes #701
jdfreder/nteract,captainsafia/nteract,nteract/nteract,nteract/nteract,rgbkrk/nteract,0u812/nteract,0u812/nteract,captainsafia/nteract,jdetle/nteract,nteract/nteract,nteract/composition,nteract/nteract,rgbkrk/nteract,0u812/nteract,jdfreder/nteract,nteract/composition,jdetle/nteract,nteract/composition,jdfreder/nteract,captainsafia/nteract,jdetle/nteract,jdetle/nteract,rgbkrk/nteract,jdfreder/nteract,temogen/nteract,captainsafia/nteract,temogen/nteract,temogen/nteract,0u812/nteract,rgbkrk/nteract,rgbkrk/nteract,nteract/nteract