Remove ssl_certificates cookbook dependency

It's now up to the user to get their certificates onto the target system
however they see fit.

We just need three attributes; 'ssl_keyfile_path', 'ssl_certfile_path',
and optionally 'ssl_cabundle_path'.

Fixes Issue #10
Merge pull request #10 from QuickbridgeLtd/feature/certs-dependency

Remove ssl_certificates cookbook dependency