setup.py change for pip-interoperability

I could not install python-bloomfilter using

```
pip install git+ssh://git@github.com/jaybaird/python-bloomfilter.git#egg=python_bloomfilter
```

That is, the install succeeds, but I could not import pybloom or its parts afterwards.

I changed setup.py and __init__.py so that setup.py install results are in line with examples given in the readme.