Observe.List.sort -- Fix build process

Fixes build process when `observe.sort` is added to list of plugins to compile.  Steal doesn't seem to like a regex next to a unary plus.

Building the sort plugin without this fix gives the error:

```
>  can/observe/sort/sort.js
YOU SHOULD NOT BE HERE
!!!!!!!!!!! ERROR !!!!!!!!!!!

-message    = Cannot find function comment in object [object Object].
-fileName   =
-name       = TypeError
-lineNumber = 0

              error loading html element  [object HTMLScriptElement]   TypeError: Cannot find function comment in object [object Object].
```

This was referenced in #189, but never fixed.  This PR doesn't resolve the underlying problem, but also shouldn't hurt anything.