Multi-column sorting

[ssorallen]

It would be nice to be able to sort by multiple columns. If two rows are equal for a given column, they will continue attempting further sorters until all Sorters are exhausted or an order is found.

The defaultSort prop could take an Array<Sorter>.

<Table className="table" id="table" data={[
    { Name: 'Lee Salminen', Age: '23', Position: 'Programmer'},
    { Name: 'Griffin Smith', Age: '18', Position: 'Engineer'},
    { Name: 'Ian Zhang', Age: '28', Position: 'Developer'},
    { Name: 'Lou Malnati', Age: '28', Position: 'Programmer'}
]}
sortable={[
    'Age',
    'Position'
]}
defaultSort={[{column: 'Age', direction: 'desc'}, {column: 'Position', direction: 'asc']}
defaultSortDescending

onSort could return an Array<Sorter> if multiple columns are being sorted.

[
  {
    column: 'Name',
    direction: -1
  },
  {
    column: 'Age',
    direction: 1
  }
]

The interaction for clicking columns would need some design consideration.