Update traverse and sequence Errors to signal for Apply and not Applicative

[evilsoft]

The Times are a Changin'

Because we are not implementing the fantasy-land methods for the public traverse and sequence methods, we only need to constrain to Apply and not as strict as Applicative as Apply returning functions are all that are needed.

So we should report that 🌽striant properly in our Errors. That, my friends, is all this PR does.

[coveralls]

Coverage remained the same at 100.0% when pulling 700ca6a on update-traverse-errors into 36bb58a on master.

[evilsoft]