add support for orderBy, without about rethink-swift

[pixelspark]

@breathe sure! I have added a swift-2.2 branch which you can submit your pull requests against. I might even try to port your patches to the swift-3 version afterwards :)

[breathe]

@pixelspark -- Awesome thanks! I've just submitted a pull request against the 2.2 branch. #4

Hopefully I'm doing things a reasonable way -- I'm super new to rethink but your code has been awesome to speed up the learning process!

[pixelspark]

#4 is merged, and I committed similar changes for Swift 3! Thanks & closing.

[breathe]

Awesome! Thanks!!