Replace VectorOps with a more general IndexedSeqOps

Pimps on `Vector` still remain, including the accidental addition of `groupWhen`.  We exploit the type relationship between `scalaz.std.indexedSeq` and `scalaz.std.vector` to have them share an `Ops` set.

```scala
scala> Vector(1,2,3).groupWhen(_ < _)
res0: Vector[Vector[Int]] = Vector(Vector(1, 2, 3))
```