Moved to Network.Nanomsg and use Tasty and 0MQ4

Hi,
I propose some changes, but these are mostly design choices, so please take them with a grain of salt:

* I think this package should be under the ```Network``` hierarchy of modules, or alternatively ```System``` (as 0MQ). Personally I think ```Network``` makes more sense, but any of those seem preferable to just ```Nanomsg```.
* [Test-framework](https://github.com/batterseapower/test-framework) seems mostly dead. While there seems to be an [active fork](https://github.com/haskell/test-framework), [tasty](http://documentup.com/feuerbach/tasty) seems to be more actively maintained. The replacement was quite direct.
* Replaced ```zeromq3-haskel``` with ```zeromq4-haskell```

Tests and benchmarks are passing and running, respectively.

What do you think?