Support sending basic auth key via headers instead of query.

Example 1 says the following about the "location" param:

> (8). "location" (optional) key value sets where the api key will go in the request. Defaults to "query".

While it "defaults" to query, there does not appear to be any other options. I have an API that sends the token via a header, so I added the option to use "header" as a location for basic key authentication.