Bug: Inconsistency in how `fromfile` and `intersection` and `union` deals with self.bitarray

[srean]

Once you deserialize a serialized BloomFilter object the self.bitarray length might differ because of added padding.

https://github.com/jaybaird/python-bloomfilter/blob/master/pybloom/pybloom.py#L271

Here difference in length due to the trailing bits is ignored.

No such accounting of differing bitarray lengths are being done here https://github.com/jaybaird/python-bloomfilter/blob/master/pybloom/pybloom.py#L224 or https://github.com/jaybaird/python-bloomfilter/blob/master/pybloom/pybloom.py#L238 . Here the bitarray union and intersection will fail if the bitarray.length( ) are different. The lengths may differ because of a roundtrip through serialization deserialization, even when the capacity and error-rates are the same.

I think the correct thing to do here is to strip off the padding in fromfile to ensure that the bitarray representation is exactly the same