Gearing up for a 1.18 release

[Johan Tibell]

Hi all,

The sandbox functionality now works well enough that I think we should
let it out in the wild. I've created a 1.18 release branch at

    https://github.com/haskell/cabal/tree/cabal-install-1.18

My intention is to make any necessary bug fixes on that branch before
the release and then merge those fixes into master once the release is
done (i.e. using a work flow similar to
http://nvie.com/posts/a-successful-git-branching-model/ but without
the develop branch).

Are there any fixes that absolutely must make it in before a 1.18
release? Remember, this release is already long overdue and there will
be more frequent releases in the future so lets not try to cram in
some extra functionality and delay this release further.

P.S. In the future I hope we can make a release every 3-6 months
instead of the current almost yearly release cycle.

Cheers,
Johan