fix re-exports arrays.js

The re-exports weren't quite right as it needs to be clear it is the `default` value which is being re-exported.

Ideally one would write this:

```javascript
export { default as compact } from './arrays/compact';
```

But this syntax wasn't working in Traceur's parser for me currently (https://github.com/google/traceur-compiler/issues/816).

To work around this, I've just imported and then separately exported, although it isn't ideal.

The good news is that it all works though with that. See the demo here - http://jsbin.com/netamihu/2/edit