Pybloomfiltermmap

- Changed prime number finder to use a standard double and add 1 to find
likely numbers in log(n) time.

- Fixed issue 5, wherein a call to open() returning an invalid fd would
cause a seg fault. [BUG]

- Added __len__ which gives a good estimate of how many elements were
inserted [FEATURE]
- Removed __ixor__ since it didn't make much sense.
- Added .intersect() and .union() as a synonym for __iand__ and __ior__ [FEATURE]
- Added reserved space to the BloomFilter structure to support future updates. [FEATURE]

- Added MANIFEST so that building distributions works [FEATURE]
- Restructured docs so that html is a symlink to the _build/html directory [FEATURE]
- Added Cython detection in setup.py. Building now works without Cython installed [FEATURE]

- Fixed bug where opening invalid bloom files caused seg faults [BUG]
- Fixed alignment bug where sometimes hash seeds would not [BUG]
be compared correctly.