Pass at documenting dynamic record support

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

Bit of general doc cleanup and refactoring while I'm in here.

Make sure both set-id and name match when finding rrset

Route53 delete orig rrset

Tinydns additions

from TinyDNS files

Update CHANGELOG.md to include new normalizations

README.md: Add "Table of Contents"

Update .gitignore to exclude setup.py generated build dir

cc #337 #346

Update link to record objects

Normalize CNAME/ALIAS/PTR value to lower-case

Refactor shell script syntax and consistency

#303 renamed records.py to records/__init__.py.

This updates docs/records.md to link to the new path.

- Add a missing space for styling
- Replace legacy "\`...\`" with `$(...)`
- Quote variable to prevent word splitting
- Use builtin `command -v` instead of non-standard `which`
- Add two missing `>&2` redirection for error/warning message

Allow multiple YAML files to define zones

DynProvider dynamic serve_count=1 to match Route53

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

We hit this bug internally. It generally needed to be fix and was a larger
potential problem than expected since it was assuming TD assocaitions rather
than looking at them directly. Test changes were a little involved to suss
out, otherwise this is a fairly clean and simple fix.

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>

Might be possible/make sense to allow it to be configured later, but for now
Route53 doesn't support it so we'll go with 1 to make sure that things match
up behavior-wise.

Signed-off-by: Christian Funkhouser <cfunkhouser@heroku.com>