Optional cython for runtime

[Artimi]

cystatsd does not have to depend on cython for user. If we include generated file cystatsd/collector/collector.cpp we can ship cystatsd without cython. However, if user has cython installed it will be used to regenerate that file. You can find information about this in http://stackoverflow.com/questions/4505747/how-should-i-structure-a-python-package-that-contains-cython-code . This is even recommended by cython itself http://docs.cython.org/en/latest/src/reference/compilation.html#distributing-cython-modules . You won't to regenerate that file when something changes because I edited implementation of sdist so the file is regenerated each time sdist is called and something in source files changed.

[scivey]

Looks solid, thanks for the PR! Going to test this out before merging, so may be a couple more days before this gets to PyPI.

[vitawasalreadytaken]

Hi @scivey, have you had time to test this? We're looking forward to releasing a fast statsd client based on cystatsd and this is hopefully our last blocker :)