Validate Record name & fqdn length

Start on supporting python3 using backwards compat bits for now

Co-Authored-By: Theo Julienne <theojulienne@github.com>

Co-Authored-By: Theo Julienne <theojulienne@github.com>

ConstellixProvider: change ALIAS to CNAME to allow record deletion

Fix 'server error: zone not found' for NS1 provider

Many providers make their modifications in the order that changes comes. In
python3 this causes things to be inconsistently ordered. That mostly works, but
could result in hidenbugs (e.g. Route53Provider's batching could be completely
different based on the order it sees changes.) Sorting changes consistently
is a good thing and it shouldn't hurt situations where providers are already
doing their own ordering. All-in-all more consistent is better and we have to be
explicit with python 3.