add out parameter

also added mkdirp as it errors when $out does not already exist.

use case:
```
raw: {
  'font-awesome': {
    src: "../node_modules/font-awesome/fonts/",
    out: "fonts",
  },
  semantic: {
    src: "../node_modules/semantic/src/fonts/",
    out: "fonts",
  },
},
``` 

cheers!