fix treeLocEqual and improve TreeLocArbitrary

Cherry-picking pull request #527
override zipWithL, zipWithR

Cherry-picking pull request #534 (1a46eb5, c5cfc46)
fix comments

Cherry-picking 4c2bd1f
optimize NonEmptyList#traverse1. avoid stack overflow

Cherry-picking pull request #539 (5f57bd6)
Deprecate Liskov#inv.

Cherry-picking bc2d3e4
fix comments

Cherry-picking e3d4704
fix scalaz.==>> bug

Cherry-picking b591cc2
Promote arbitrary ==>> to scalacheck-binding.

Cherry-picking c7b6393
update tests for `==>>` to f719645