- This reworks the CallerReference structure for Route53 health checks in a
  non-backwards compatible way. This means records will create new healthchecks
  for themselves which should be fine.
- Since we're pre 1.0, support has NOT been added to cleanup the old
  healthchecks. That could be done reasonably easy, BUT we'd have to keep that
  around forever. The hope is that the new ref format/usage will prevent this
  problem going forward since enough info exists in the ref to identify things
  fully. :fingers_crossed:
- healthcheck GC is much cleaner and more robust thanks to ^
- overall the healthcheck management code is a bit easier to follow and more
  robust now.

Alias support

Add support for ignored records.

Escape unescaped semicolons coming out of Route53

Fix zone-level always-dry-run functionality

Thanks @offmindby!

```yaml
ignored:
  octodns:
    ignored: true
  type: A
  value: 1.2.3.4
```

DnsimpleProvider updates delete before create, or else errors thrown

NS1 does not support SSHFP

Supports ALIAS for Dnsimple, Dyn, Ns1, and PowerDNS. Notes added to readme about
some of the quirks found while working with them. TTL seems to mostly be
accepted on ALIAS records so it has been added back, what it means seems to vary
across providers, thus notes.

Fix NS1 provider name

Update example class name from "octodns.provider.nsone.Ns1Provider" to working "octodns.provider.ns1.Ns1Provider".

Update README to include new NS1 Provider

First pass through NsOneProvider

Add __main__ calls to main in cmds

Fixing octodns/record.py link

use a percentage of change/deleted records rather than an absolute count

Dyn monitor user agent

Route53 geo conv fixes