support_tags should have option for "true", "false", and "read_once"

[ewah]

Tags will be dynamically polled by the hook as "branches that don't change".

The above from the readme is not true. git2consul will continually poll (git pull) the tag's to find it's ref.

There should be support for 3 modes.
false - do not look for tags at all
true - look for tags, and always poll for changes to tags
read_once - look for only new tags, but do not pull them once they have been loaded.