py-bitarray: updated to 2.7.0

2.7.0:
-------------------
* add `util.sc_encode()` and `util.sc_decode()` for
  [compression of sparse bitarrays](sparse_compression.rst)
* add `util.any_and()`
* add `util.intervals()`
* move functionality of the following utility functions entirely to C:
  `hex2ba()`, `base2ba()`, `deserialize()`, `vl_decode()`, `zeros()`
* improve error checking for unpickling
* add [distance metrics](../examples/distance.py) example:
  dice, hamming, jaccard, kulczynski1, rogerstanimoto, russellrao,
  sokalmichener, sokalsneath, yule
* add example [sparse bitarray](../examples/sparse) implementations

(adam)