Skip cert verification for test

cc @jch as I'm unsure if we want to go this route or make the cert verifiable instead
Cache cacert.pem for local testing, wire up override, VM-aware path
Merge branch 'master' into starttls-test-verify-none
Add verify none test, differentiate
Merge pull request #166 from ruby-ldap/starttls-test-verify-none

Specify certfile to verify SSL certs against in tests