Resizable: alsoResize more than one element of a jQuery selection

Fixes #4666.

Did not cause any (new) tests to fail. Several tests were failing on my machine when I pulled the project and set up per the readme (including two [unrelated?] resizable tests).

The selector syntax used in the implementations of `_store` and `_alsoResize` appear to be semantically identical to the removed code (sans the `o.alsoResize[0]`) and function as expected in my personal use.