mout/mout — pull request #36 by MathiasPaumgarten (2013-02-06 18:35:56+00:00)
Title: fix number/sign

I changed number/sign to return `0` when the argument is `0`.

The definition of sign goes as follows:

```
1 if x > 0
sign(x) = 0 if x = 0
-1 if x < 0
```

[Wikipedia](http://en.wikipedia.org/wiki/Sign_(mathematics)