Stop advising the creation of certificates with a blank subject.

In jruby OpenSSL::X509::Certificate.new will raise the following error when
the certificate has a blank issuer, which is copied from the subject for a
self-signed certificate.

OpenSSL::X509::CertificateError: Empty issuer DN not allowed in X509Certificates

Adding an organization to the subject avoids this error.
Merge pull request #8 from Shopify/avoid-blank-cert-issuer

Stop advising the creation of certificates with a blank subject.