Compare plain perl data structures with Test::Deep

Hi Philip,

I'm trying to verify perl datastructures ala:

```
$s3->expects('put')
   ->with('test-bucket', 'test-id', 'my data', {})                              
   ->returns(1);
```

but it would always fail because it uses `eq` to compare everything. What do you think about doing a deep comparison instead? Can Test::Spec already do this?

I'm happy to update the docs etc but wanted to get your thoughts before jumping in

It is a nice little module, thanks for it.

Andy