ChainRules tests are failing on 0.9.4

[oxinabox]

e.g. https://travis-ci.org/github/JuliaDiff/ChainRules.jl/jobs/673580313

Looks like real differences, so I think something is still broken that wasn't fixed by #68

@willtebbutt are you able to investigate by doing the whole
] dev ChainRules FiniteDifferences
] test ChainRules

thing?

[willtebbutt]

Yup. Will take a look in the morning.

[oxinabox]

thank you (feel free to leave it til tuesday if that is better for you)

[nickrobinson251]

resolved by #71