v0.6.0

The 0.6.0 CNI release is a major packaging release, with some minor bugfixes and improvements to the Go implementation.

Important: the plugins have been separated to a separate repository. You should update any build scripts accordingly. This repository contains only the golang implementation of the spec, for use in plugins and runtimes.

This release does not change the spec, which remains at v0.3.1.

Many thanks to the 20 contributors who helped make this release possible.

Documentation & Convention changes:
#427 Conventions: add convention around chaining interfaces
#487 README plugins list: add Linen CNI plugin
#473 Update and document release process
#472 Add CNCF reference in README
#465 Add Code of Conduct
#430 Update main title from "Proposal" to "Specification"

Other changes of note:
#482 cnitool: add support for CNI_ARGS
#481 scripts/release.sh: Add in s390x architecture
#460 pkg/types: return error instead of crashing when code supplies an incompatible type to types.LoadArgs()
#477 types: fix marshalling of omitted "interfaces" key in IPConfig JSON
#475 pkg/invoke: backfill tests of delegate add & del
#406 Return cni.type.Error instead of plain error
#470 Vagrantfile updates
#464 pkg: move packages from cni to plugins
#461 pkg/invoke: ensure that custom env vars are prepended to the env
#465 Add Code of Conduct
#457 plugins: moved to containernetworking/plugins
#450 cniVersion and config structure mismatch
#445 Add cniVersion to Result
#433 scripts: cleanup() should rm net container in docker-run.sh
#440 cnitool: support capablity args