Width of selectize and sliders

This PR does not smell good to me, but I do not see another approach for specifying the width of selectize/sliders. The problem is, it won't work if we specify the width of their original input elements (`<select>`/`<input>`), and selectize inputs / sliders are rendered dynamically later. I had to use `.css()` on the next sibling of the original inputs. Neither selectize nor sliders has the API for specifying the width.

@jcheng5