Reference correct version of Sweet in docs

[tomByrer]

I see you have a new v2, but the (HTML) docs all seem to still on v1? I'd prefer to learn v2 straight away, then have to unlearn things I might like from v1 ;)

[disnet]

Haha, sorry about that, the docs say 1.0 but mean 1.0+. We should fix that.

[tomByrer]

Cool thanks. Might be helpful to tag the doc blocks when a feature is added, since 2.0 2.1 added something significant. Used when maintaining old software (I needed in lodash.