OpsWorks connect_to_region helper caused TypeError exception

Previously the opsworks.connect_to_region helper would throw an exception:

```
  File “…/boto/opsworks/layer1.py", line 99, in __init__
    super(OpsWorksConnection, self).__init__(**kwargs)
TypeError: __init__() got an unexpected keyword argument 'region'
```

This was due to OpsWorksConnection passing along its region parameter into the superclass, which didn't expect it. (This would also happen if you passed in a region parameter directly to OpsWorksConnection.)

I added a simple fix for this as well as another simple test for the regions() helper.