ListT.underlying should be run, to be consistent with other transformers.
Add Validation.failNel for creating a ValidationNel

Because Validation.failure(NonEmptyList(x)) just feels so verbose
Add deprecated underlying method to help ease the transition to run.
Merge pull request #720 from ceedubs/validation-failnel

Add Validation.failNel for creating a ValidationNel
Merge pull request #719 from shawjef3/scalaz-seven

ListT.underlying should be run, to be consistent with other transformers...
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