Update client to support latest API behaviors / data; v0.5.0

[theckman]

This change updates the package so that it continues to work with the ipdata.co
API. This also introduces breaking changes in the interest of simplifying the
code and reducing the API surface area.

There were some changes made to the dara structure returned over the JSON API
from ipdata.co, as well as how the authentication credentials are provided to
the API itself. This change primarily was executed to support the new format and
authentication mechanism.

Specifically, some string fields were converted to Objects within the ipdata.co
API to provide more rich data. Things like the timezone, the currency, and the
risk/threats associated with that IP. The API also stopped accepted
authentication tokens via HTTP headers, and now requires them via URL query
parameters.

In addition to that, the idea of using one struct type for the JSON
communication and another for consumers of this package to use has been
backed-out. The original implementation used a RawIP struct for communication
to JSON, and then would convert it to an IP struct while doing things like
parsing timestamps in to time.Time, timezones in to *time.Location, and
converting URLs to *url.URL.

Instead of assuming everyone would want the URL to be a *url.URL, or that they
really need to parse the timestamp, we now only deal with the serialization and
deserialization from the API. We leave it up to consumers to parse the data in
to a different type if they choose to do so.

So the IP struct was removed, and the RawIP struct was renamed to IP.
Also, all of the RawXXX functions and methods were removed.

Signed-off-by: Tim Heckman t@heckman.io