Support direct nesting

[Eric Eastwood]

Add support for the use of the & by itself (without @nest rule): http://tabatkins.github.io/specs/css-nesting/#direct-nesting

nesting selector, written as an ASCII ampersand &.

A style rule can be directly nested within another style rule if its selector is nest-prefixed.

[Jonathan Neal]

Thanks for making an issue for this, @MadLittleMods. Yes, the spec allows for direct nesting, meaning no @nest at rule, but only when the explicit & is the first character.

[Tom Bremer]

I can make pull request for this if it's something you are interested in supporting…

[Jonathan Neal]

I would be. I may not have the time to make it myself in the next day or two.

[Zoë Bijl]

+1