fix(encoding): Handle invalid encoding

[fjg]

This is due to Faraday response.body which is set to ASCII-8BIT instead of (request header charset, i.e. UTF-8).
Seams related to a underlying adapter: see lostisland/faraday#139

[coveralls]

Coverage remained the same at 96.166% when pulling e4b4dfd on fjg:invalid_encoding into fb502c7 on intridea:master.

[coveralls]

Coverage remained the same at 96.166% when pulling 48dc305 on fjg:invalid_encoding into fb502c7 on intridea:master.

[coveralls]

Coverage remained the same at 96.166% when pulling b02401b on fjg:invalid_encoding into fb502c7 on intridea:master.

[sarojkh]

The issue this PR is trying to solve seems to have been already solved by #271, and then rervamped by #380.

@josephpage This PR might as well be closed.

[pboling]

@sarojkh Thanks for reviewing!