Use versioneer

  * edit `setup.py` to include the versioneer configuration code and use it in the setup call
  * `versioneer-install`
  * `setup.py versioneer`
  * modify `newsbuilder/__init__.py` to add `__version__` to `__all__`
Try making the file-reading helper in setup.py ${CWD} agnostic.
Avoid clobbering globals - so we can use them.
Perhaps relative paths are a red herring.  How about an explicit MANIFEST.in mention?
Fix a pyflakes error in generated code from an upstream project... because otherwise the pyflakes build turns red.
Also include the LICENSE file!
Also include the tox configuration.
Merge pull request #22 from exarkun/versioneer-17

Use python-versioneer to define the package/software version.