nex3/sass — pull request #550 by fd (2012-10-24 12:47:15+00:00)
Title: Allow un-/defining custom unit conversions

Define a new unit `foo` in terms of `px`:

```ruby
# sass/scss config
Sass::Script::Number.define_unit 1, "foo", 42 "px"
# signifying 1foo == 42px
```

Then use `foo`:
```scss
div {
height: 2foo;
}
```

Which produces:
```css
div {
height: 84px;
}
```

The idea is that (eventually) one could define a custom unit like so:

```scss
@unit 1foo == 42px;
```