Change: Don't hard code SSL certs or paths

Because we need to be able to use this cookbook for various
environments, it's important to be able to link the SSL hosts
and the vhost, so we don't want a hard-coded one, which was fine
for proof of concept.
Change: Use the vhost name to render the SSL directive

The SSL config for each vhost will make the conventional
assumption that the SSL cert is named per the vhost definition
and is found in /etc/nginx/ssl.
Improvement: Support enable, disable, create, delete

This is a major refactor of the provider code.  It now supports
four actions:

- :enable
- :disable
- :create
- :delete

We also now hand over indempotence checks to the underlying
providers as we aren't doing anything that requires our own
custom check.
Version bump
Update Changelog
Merge pull request #3 from Atalanta/ssl-improvements

Ssl improvements