Implement "chunked" TXT/SPF value support for long values

This implements it transparently at Record level. Providers that need things to
be chunked (seems to just be Route53 an Dyn) switch to use `chunked_values`, but
everything else can stick with `values`. I've run through each provider I have
access to verifying that things operate as expected/required. OVH and Azure are
untested.

0.8.7 release

`Included` and `Excluded` can be used to filter records for one or more specific provider(s). This can be extremely useful when certain record types are not supported by a provider and you want only that provider to receive an alternative record.

See also: https://github.com/github/octodns/issues/26

Add OVH as octodns provider

Add an octoDNS provider for rackspace.

Cut v0.8.6

Fixes for cloudflare CAA support

CAA support

Seem to be pretty inconsistently implemented/validated across providers so
just shrug and move on.

Add support for increasing Route53 retries

Fixed TXT record bug when creating the record with Azure

Allow proto to be specified for powerdns

This allows a scheme to be set for the PowerDNS API. It defaults to
http to retain backwards compatibility.

Improved/actionable keys out of order error message

Release v0.8.5

Fix major performance issue with add_record O(N^2)