Doesn't work with ueberauth 0.7.0

[Tom]

Authentication callback fails with CSFR error.

%Ueberauth.Failure.Error{message: "Cross-Site Request Forgery attack", message_key: :csrf_attack}

[Hans]

Hi @tomsharratt.

This is linked to change made here ueberauth/ueberauth#136
Something like this needs ueberauth/ueberauth_facebook#65 needs to happen for the slack client aswell.

More docs can be found here https://github.com/ueberauth/ueberauth/blob/7ebc0aeeb17d0953bdc53a01018307fb03e0b189/lib/ueberauth/strategy.ex#L265

[Steven Fuchs]

Great work on this! Works like a charm. Any chance you could push this new version to hex? TIA