Remove id dependency

@kenearley @stof @koenpunt

Some time ago, we made a change in Chosen that made the plugin less dependent on HTML IDs. This had two major benefits: 1) the code became less brittle and 2) it became possible to initialize Chosen outside of a DOM context. Chosen still has some remnants of this ID requirement and I've finally gotten around to cleaning them up in this PR.

Notes about this PR

- IDs are no longer required on any element within Chosen.
- The function that generates random IDs for jQuery selects has been ripped out.
- If the select Chosen is being applied to has an ID already, Chosen still adds an ID to its container as I have found this functionality useful.
- There is a lot of red in this PR :boom: