Use query params for GET requests

GET requests are [not allowed to have a body](http://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4.3), although curl is a bit of a rebel and allows it.

Rather, for GET requests that need to provide options, we should be providing them as params.

In order to maintain backwards compatibility, however, I merge `req.body` and `req.query`, with `req.query` taking precedence.

Hopefully my influx in pull requests is more helpful than it is annoying :)