Ratio docs

[avelinet]

Status: Ready to merge

Reviewers: @kpeatt @jeffkamo @ry5n

[jeffkamo]

Other than my comment, +1

[ry5n]

We should probably link to some background on the technique and some use cases:

• http://alistapart.com/article/creating-intrinsic-ratios-for-video.
• http://daverupert.com/2012/04/uncle-daves-ol-padded-box/

Could also expand the description, maybe something like this:

Fluid-width element with an intrinsic width/height ratio. Can also be used to fit make video content fit the width of its container. Also works well for featured areas with small and predictable text content – for example, a hero block with a background image and (maybe) a title.

Ratio is square by default and ships with 4 × 3 and 16 × 9 ratios as modifier classes. Create custom ratios by defining additional modifiers.

[ry5n]

Once the above comments are addressed, +1 from me.

[jeffkamo]

Comments have been addressed. Ready to merge!