Pybloomfiltermmap

- Fixed memory leak in SHA512 computation. Thanks pbutler! [BUG]

- Fixed segfault when using non-strings as values. [BUG]

- Fixed casting of size_t for very large bloom filters. [BUG]
- Added option to use standard memory (rather than mmap) to back the bloom filter.
(Specify None or '' as the argument to file name.) [FEATURE]
- Changed hash to use a "superfast" hash rather than md5 since md5 is
unnecessarily slow. [FEATURE]

- Fixed hashing to use md5 hash and change the bit computation to pass
accuracy test. [BUG]

- Added check to ensure that the required permissions are available when
opening a file. [BUG]

- Added __dealloc__ to fix memory/resource leaks. [BUG]
- Added .close() method to forcibly close a bloom filter object. [FEATURE]