declare package data in a way that is compatible with wheel packages

[eroldan]

This patch fixes package data not being found when installed from wheels. The "package_data" declaration seems to be the most current compatible way in the confusing distutils/setuptools world.

Example error:

[root@node-1 wheelize]$ ./edo/bin/gateone --version
Traceback (most recent call last):
  File "./edo/bin/gateone", line 7, in <module>
    from gateone.core.server import main
  File "/root/wheelize/edo/lib/python2.7/site-packages/gateone/core/server.py", line 398, in <module>
    from gateone.auth.authentication import NullAuthHandler, KerberosAuthHandler
  File "/root/wheelize/edo/lib/python2.7/site-packages/gateone/auth/authentication.py", line 86, in <module>
    from gateone.core.locale import get_translation
  File "/root/wheelize/edo/lib/python2.7/site-packages/gateone/core/locale.py", line 25, in <module>
    a for a in resource_listdir('gateone', 'i18n')
  File "/root/wheelize/edo/lib/python2.7/site-packages/pkg_resources/__init__.py", line 1196, in resource_listdir
    resource_name
  File "/root/wheelize/edo/lib/python2.7/site-packages/pkg_resources/__init__.py", line 1487, in resource_listdir
    return self._listdir(self._fn(self.module_path, resource_name))
  File "/root/wheelize/edo/lib/python2.7/site-packages/pkg_resources/__init__.py", line 1575, in _listdir
    return os.listdir(path)
OSError: [Errno 2] No such file or directory: '/root/wheelize/edo/lib/python2.7/site-packages/gateone/i18n'


[root@node-1 wheelize]$ ./edo/bin/pip list
backports-abc (0.4)
backports.ssl-match-hostname (3.5.0.1)
certifi (2016.8.8)
futures (3.0.5)
gateone (1.2.0)
html5lib (0.999999999)
pip (8.1.2)
setuptools (25.1.6)
singledispatch (3.4.0.3)
six (1.10.0)
tornado (4.4.1)
webencodings (0.5)
wheel (0.29.0)