Added :host ("ezid.cdlib.org") and :use_ssl (`true`) options to Client config.
Private API between Client and Request tweaked to maintain separation (i.e, so
that Request does not need access to Client): Request initializes with a full
URI rather than just a path.
Closes #15
Merge pull request #18 from duke-libraries/15-host-option

Added :host ("ezid.cdlib.org") and :use_ssl (`true`) options to Client config