Use of arbitrary Python objects

I think it would be pretty cool/useful to allow arbitrary Python objects in `pydablooms`.

This change is based on `hash` function return values just like in other container data structures.

```python
>>> import pydablooms
>>> bloom = pydablooms.Dablooms(1000, 0.05, '/tmp/bloom.bin')
>>> bloom.add('hey thar!')
1
>>> 'hey thar!' in bloom
True
>>> bloom.add((2, 3, 5, 7))
1
>>> (2, 3, 5, 7) in bloom
True
>>> (2, 3, 5, 7, 11) in bloom
False
>>> bloom.add([1, 4, 9, 16, 25])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'
```

Assuming this proposed adjustment is desired functionality, it would also fix [issue 58][1] and render the corresponding pull request unnecessary.

[1]: https://github.com/bitly/dablooms/pull/58