"core" snap in the candidate channel updated

[Michael Vogt]

Hi,

this is just a quick heads up that we updated the "core" snap to snapd
2.18.1 in the candidate channel to include the following important
bugfixes:

- daemon: fix crash when `snap refresh` contains a single update

This is a regression that can block updates under certain conditions.

- fix unhandled error from io.Copy() in download()

This is a one-liner that improves the error reporting for certain
download failure conditions. The current 2.18 can give really
misleading error messages on e.g. premature connection closing during
a download.

- interfaces/builtin: fix incorrect udev rule in i2c

This fixes the i2c interfaces, without it that interface is not
working properly.

The release for this Thursday (8.12.2016) is unaffected by this. We
plan to release this candidate "core" snap as the stable "core" snap.

Cheers,
 Michael