Lowered upper bound on binary

As promised :)
I'm using a CPP ifdef so no mods to the cabal manifest are needed. 
Tested into a sandboxed environment and all tests pass except for one, where I get:

```
1) ConnectionSpec.openConnection, with custom vhost and valid credentials, connects successfully
uncaught exception: AMQPException (ConnectionClosedException "Handshake failed. Please check the RabbitMQ logs for more information")
```

But it seems more a misconfigured environment of mine than a regression.

I took the freedom of **bumping the cabal version** and just pretty formatting 
packages in the manifest. Relaxed binary boundary to use >= 0.5.

An hackage upload would be really appreciated, if everything satisfies you :)

Alfredo