Updated deprecated adapter example
This example of setting the middleware for an api client throws the following compile errora
** (CompileError) lib/integration_tester/aversion_client.ex:7:
Adapter aliases and local functions has been removed.
Use full adapter name or define a middleware module Hackney
adapter :hackney
See https://github.com/teamon/tesla/wiki/0.x-to-1.0-Migration-Guide#dropped-aliases-support-159