Fix Frank JWT decode

[ghost]

The function decode has changed to Frank_jwt and needs 4 parameters

[TatriX]

Thanks for the PR.
It's a bit strange though that on travis it tried to compile frank_jwt v3.1.2 when it has an explicit version of 3.1.1 in Cargo.toml. It would be nice to find out how this happened in the first place to prevent this from happening in the future.

[TatriX]

Ok, my bad:

... 0.1.0” does not mean exactly 0.1.0, it’s a synonym for “^0.1.0”. You want “=0.1.0” to get exact.

[ghost]

Thats true
I have the same problem on my Localen computer.
the version from Cargo.toml is ignored.

The string "3.1.1" is a semver version requirement. Since this string does not have any operators in it, it is interpreted the same way as if we had specified "^3.1.1", which is called a caret requirement.

[ghost]

Ok, my bad:

... 0.1.0” does not mean exactly 0.1.0, it’s a synonym for “^0.1.0”. You want “=0.1.0” to get exact.

Found the same :)