Warnings and a non-working demo

[mandolyte]

When Styleguidist is run, the following warnings are shown:

./src/components/datatable/DataTable.context.js
  Line 2:45:   'useCallback' is defined but never used
                            no-unused-vars
  Line 143:7:  React Hook useMemo has an unnecessary dependency: 'data'. Either exclude it or remove the dependency array  react-hooks/exhaustive-deps

After Styleguidist is running, click the "Cell" demo link in the left nav area. The page shown has two demos. The first one looks ok. The second is titled "Row Header Example". The component is not rendering anything.