fully qualify python-instagram imports. fixes snarfed/bridgy#285 and snarfed/bridgy#286.

when i moved interpret_http_exception() to oauth-dropins in snarfed/bridgy@89132d2c4ff96f6367a1a0df213d987953b0a7aa and snarfed/oauth-dropins@321c3f817b838030ad6dda1211e7a23797a8c5cf, i fully qualified all of the python-instagram imports in bridgy and oauth-dropins, but not in this repo, so classes like InstagramAPIError ended up duplicated since they were imported twice under different paths, so the classes didn't match in the except clauses in interpret_http_exception(). ugh.