1.2.0

An empty api_key sends no Authorization header.

Bearer with nothing after it is not a credential, so an endpoint that parses
the header answers 400 or 401 to it. A client built with JevClient("") now
leaves the header off the request, which is what an endpoint that asks for no
credential expects. A non-empty key is unchanged.

Measured against a local server: "a-real-key" sends Bearer a-real-key, ""
sends no Authorization header.