Various fixes

* The `#put` and `#post` methods were broken; change them to accept `data` arguments and pass them correctly to Faraday.
* Allow for optional omission of the URL's host in the HTTP methods.
* Adopt a convention to use a hash for specifying optional query string key/value pairs. Uses Addressable.
* Allow the user to specify dates as Chronic-parseable strings, UNIX timestamps, or `Time` objects.

I should've broken these up into separate commits, but many of them are related. If you want to apply some but not all, let me know and I'd be happy to submit a new PR.