next pass at content_style: 'fit' | 'grow'

[chriddyp]

Perhaps this behaviour can be integrated via a set of documented style parameters in the style_table property.

[chriddyp]

With the new defaults (content_style: 'grow', style_table: {'width': '100%'}), I found that I haven't needed to use fit yet. In fact, none of the examples in the docs use this.

[alexcjohnson]

🔪 in #446 - though we missed it in the changelog and migration guide. Added to the changelog 6721d03, migration guide edit to follow.