Pyprobables

* Remove **Python 2.7** support

* Fix `RotatingBloomFilter` to keep information on number of elements inserted when exported and loaded. [see PR 50](https://github.com/barrust/pyprobables/pull/50) Thanks [dvolker48](https://github.com/volker48)

* Add additional __slots__
* Minor improvement to the hashing algorithm and strategy

* Bloom Filters:
* Import/Export of Expanding and Rotating Bloom Filters
* Fix for importing standard Bloom Filters

* Bloom Filter:
* Added Rotating Bloom Filter implementation

* Added an Expanding Bloom Filter implementation
* Currently basic without import/export functionality
* Automatic expansion