[Fab-user] [ANN] 2.4 out with some new upgrade-friendly constructors

[Jeff Forcier]

https://twitter.com/bitprophet/status/1040372439065063424

tl;dr: if you're upgrading larger codebases piece by piece, you can now
generate v2 API objects from your v1 state (by handing it your v1 `env`
object). Requires installing both versions in the same environment (which
has been supported since 2.0; see
http://www.fabfile.org/upgrading.html#running-both-fabric-versions-simultaneously
).

This addition makes it a lot easier to start using Fabric 2 for new code
without being forced to update legacy code immediately 👍

As always, the changelog is at http://www.fabfile.org/changelog.html -
there are bugfix releases out too.

Cheers,
Jeff