async function getTableSchema(controllerUrl, tableName) {
  return getJson(`${controllerUrl}/tables/${tableName}/schema`);
}
Get schema for supplied table

Returns 
{
      schemaName: 'baseballStats',
      dimensionFieldSpecs: [
        { name: 'playerID', dataType: 'STRING' },
        { name: 'yearID', dataType: 'INT' }
      ],
      metricFieldSpecs: [
        { name: 'playerStint', dataType: 'INT' },
        { name: 'numberOfGames', dataType: 'INT' }
      ]
    }

@param {string} controllerUrl
@param {string} tableName