Add support for LiveScript

Now `nodemon` also support `.ls` (LiveScript) files). 

```
 _ _                          _       _   
| (_)_   _____  ___  ___ _ __(_)_ __ | |_ 
| | \ \ / / _ \/ __|/ __| '__| | '_ \| __|
| | |\ V /  __/\__ \ (__| |  | | |_) | |_ 
|_|_| \_/ \___||___/\___|_|  |_| .__/ \__|
                               |_|        
```