add a proper Readme file

Ignore-this: 1223e0a7a22ae500ef50652f8f0091ba

darcs-hash:20130920151220-3a4db-4c9974163377956e4f7d1d2d6b595c28a4993e18
add proper stuff for distributing using distutils

Ignore-this: 7fc33373e8cdbe3926206b2c119a2a1a

darcs-hash:20130920152426-3a4db-ab495269af34068616ca5dc2a0b29efa1a738528
add cythoned c file to manifest

Ignore-this: 1de7862f753e96d2071d87adabc38eda

darcs-hash:20130920160651-3a4db-257f6ff4061c1bea39e3108220b2fa077482b9ab
(README - minor improvements)

Ignore-this: e3cfa36f9cc6823540e5579174f80ae6

darcs-hash:20130920193428-3a4db-6a0e6367960dd1c999ff98025b398a7c19720cf7
setup - cope reasonably gracefully with both development (code obtained from github) and distribution (code obtained from pypi)

Ignore-this: e8bab2959b8c533f54b3e6d870f9a880

darcs-hash:20130920194202-3a4db-f2489e1fd7b91522912272b16021c4a242eaf745