Adding using to ActionT

Adding using to ActionT
Thanks for the example. I can see that `for` is quietly skipping unmatched elements
```scala
> val list: List[Any] = List((1,2), (3,4), 1, (4,5))
> for { (a, b) <- list } yield a
> res: List[Any] = List(1, 3, 4)
```
Maybe another reason to check conversions to `Any` with WartRemover.

@markhibberd ^^^