JsonArray should implement Collection [patch]

```
JsonArray should implement the Collection interface. This will allow it to be
used with other standard libraries, such as Apache Commons's CollectionUtils
and Google Guava's Collections2.

This patch is a minimally-viable product to implement Collection. It
implements all required Collection operations, and throws an
UnsupportedOperationException for all optional operations. It also includes a
test case to guarantee backwards compatibility with the Iterable interface.
```

Original issue reported on code.google.com by `cab...@gmail.com` on 17 Feb 2014 at 4:16

Attachments:
- [jsonarray_implements_collection.patch](https://storage.googleapis.com/google-code-attachments/google-gson/issue-560/comment-0/jsonarray_implements_collection.patch)