BUG: Table.sort_order didn't retain Table.type

Calling Table.sort_order on a Table would return a seemingly identical
table the only difference was that the returned value would have a
Table.type of None regardless of whatever that inital value was.

I've also added an Examples section to this method.
Merge pull request #474 from ElDeveloper/sort-order

BUG: Table.sort_order didn't retain Table.type