Support unequal width grid columns

Although the Grids page in the IU Style Guide doesn't mention this explicitly, the IU Framework CSS has support for unequal width columns such as two-thirds + one-third.

Some relevant CSS Classes from iu-framework.css

.one-half
.one-third
.two-thirds

From studying the CSS structure, there are additional special handlers for layout of images in the Image Essays chunk and for fixing chunks that typically have floated media items, like Pullquotes / Callouts, and "details" (not sure where used?).

There is an example of a Callout with Image in a two-thirds and one-third layout on the Callout Chunk
page (screenshot below).