fix Route53Provider to tollerate multiple separators in record values

Add Constellix Provider

Add Selectel as OctoDNS provider

Co-Authored-By: Ross McFarland <ross@github.com>

Adding support for Akamai's fastdns

Fix typos across octodns repository

Co-Authored-By: Ross McFarland <ross@github.com>

Co-Authored-By: Ross McFarland <ross@github.com>

Co-Authored-By: Ross McFarland <ross@github.com>

Add MythicBeastsProvider to README

Support for Mythic Beasts DNS API

- added unit tests for apply functions
- added another json config file for this
- 100% code coverage reached

- added test cases for test_apply, testing for basic create, update, delete records
- added previous state json file in test/fixtures to do the above

- added test cases for testin populate()
- added mock request responses in tests/fixtures/
- updated requirements.txt to require edgegrid-python

- fixed exception handling in AkamaiClientException
- fixed zone_records and zone_recordset fxns in AkamaiProvider and AkamaiClient
- refactored _build_zone_config in AkamaiProvider

Render README on pypi as markdown, update twine, fix a couple README bits

v0.9.6 version bump and CHANGELOG updates

Drop dynamic record value weight to 0-16

That's all Dyn supports and it's cleaner to match it than to scale dyn since
we'd lose precision we can't get back during populate.