scalaz/scalaz — pull request #130 by folone (2012-08-10 20:31:13+00:00)
Title: Fixed Validation's Monoid instance.

Followup to #129.
I've added a check for monoid laws to `Validation`'s tests, and found out, the identity element is wrong. Which resulted in things like:

```scala
scala> List(1.success[String], 2.success[String]).suml
res12: scalaz.Validation[String,Int] = Failure()

scala> List(1.success[String], 2.success[String]).concatenate
res13: scalaz.Validation[String,Int] = Failure()
```

So, I've fixed it. This is how it is now:

```scala
scala> List(1.success[String], 2.success[String]).suml
res0: scalaz.Validation[String,Int] = Success(3)

scala> List(1.success[String], 2.success[String]).concatenate
res1: scalaz.Validation[String,Int] = Success(3)
```