.frow .nowrap by default?

Personally I'm finding myself using `.nowrap` more and more frequently. As CSS Grid eats away at the old `.col-` systems, and Frow's (awesome) existing `.shrink-0` and `.grow-1` classes make working with nowrap more common, I'm debating making it the default.

This would require the `.col-` system to be altered, as the user would have to add the `.wrap` class to the containing`.frow`. Perhaps add a new rule to enable the use of columns?

Start by locating the Sass rules for `.frow`, `.nowrap`, `.wrap`, `.col-`, `.shrink-0`, and `.grow-1`. Compare how the current column system handles wrapping, then clarify the intended default and override behavior before changing it. Done means the default nowrap behavior and the `.wrap` or column-related behavior are both defined and verified.

Written by the indexing model from the issue text.