Allow an Array of jQuery objects for radioGroups and checkBoxGroups

We are creating all of our DOM functionally without templates and often deal with Arrays of jQuery objects before we attach them to the DOM tree. Right now Bacon.js does not support Arrays of jQuery objects as arguments for radioGroupValues and checkBoxGroupValues, so we would have to do this:

```
asGroup = ($elements) -> _($elements).reduce(((group, $element) -> group.add($element)), $())
stream = Bacon.$.checkBoxGroupValue(asGroup($inputs))
```

This patch removes the need to convert an Array into a single jQuery object, but keeps existing functionality intact, so you can still use a single jQuery object as input as well as an Array.