don't assume setup.py is run from its directory

when looking for the path to the regexes.yaml file, look relative to the
top directory containing setup.py, but don't assume it's the current
directory.
error out if regexes.yaml isn't where we expect it to be

better to blow up on install, then to install cleanly, but blow up when
somebody tries to use us.
Merge branch 'master' into py-setup-fix-again
Install regexes.yaml correctly

This fixes #209, the annoying issue where user_agent_parser
fails at runtime because it can't find regexes.yaml or regexes.json.

Seems to work for:
* `python setup.py develop` in ua-parser itself (as before)
* `python setup.py install` in ua-parser itself (as before)
* `python setup.py install` in some *other* package that
  depends on ua-parser
* `pip install ua-parser`
Fix 'python setup.py install' on Linux; clean up.

* 'python setup.py install' works
* 'python setup.py develop' works
* 'pip install ua-parser' does NOT work (yet)
Fix 'pip install ua-parser'
Merge pull request #268 from georgevreilly/py-setup-build_py_run

Install regexes.yaml correctly