Add SSL support that defaults to OpenSSL::SSL::VERIFY_PEER

This pull request adds two new attributes for HTTPS support:

- `verify_mode`
- `ca_file`

If `scheme` is set to `https`, `verify_mode` mode and `ca_file` can be set to alter the certificate verification type and the certificate location. Valid options for `verify_mode` are `peer` and `none`. These map to `OpenSSL::SSL::VERIFY_PEER` and `OpenSSL::SSL::VERIFY_NONE`.