Added unordered-containers to deps and strict hashmap instance

I'd like to use a strict `HashMap` instead of `Map` w/ `acid-state` since it is a more performant data structure (according to these benchmarks: http://gregorycollins.net/posts/2011/06/11/announcing-hashtables). Figured adding the `safecopy` instances directly to the safecopy package would be a good idea. The dependency on `unordered-containers` shouldn't be a problem since it's a widely used package, but let me know if you think otherwise. Version bump included.