EphemeralStream.iterate doesn't include the start value

Before:

```
scala> scalaz.EphemeralStream.iterate(0)(_ + 1).take(5).to[Vector]
res6: Vector[Int] = Vector(1, 2, 3, 4, 5)
scala> Stream.iterate(0)(_ + 1).take(5).to[Vector]
res7: Vector[Int] = Vector(0, 1, 2, 3, 4)
```

After:

```
scala> scalaz.EphemeralStream.iterate(0)(_ + 1).take(5).to[Vector]
res0: Vector[Int] = Vector(0, 1, 2, 3, 4)
```

Thanks goes to @betehess for discovering the bug.