Fixing version calculation

[anemitz]

======================================================================
ERROR: Failure: NameError (global name 'VERSIONs' is not defined)
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Traceback (most recent call last):
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/nose/loader.py", line 390, in loadTestsFromName
    addr.filename, addr.module)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/nose/importer.py", line 39, in importFromPath
    return self.importFromDir(dir_path, fqname)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/nose/importer.py", line 86, in importFromDir
    mod = load_module(part_fqname, fh, filename, desc)
  File "/Users/anemitz/Dropbox/projects/mongoengine/tests/test_dereference.py", line 6, in <module>
    from mongoengine import *
  File "/Users/anemitz/Dropbox/projects/mongoengine/mongoengine/__init__.py", line 23, in <module>
    __version__ = get_version()
  File "/Users/anemitz/Dropbox/projects/mongoengine/mongoengine/__init__.py", line 21, in get_version
    return '.'.join(map(str, VERSIONs))
NameError: global name 'VERSIONs' is not defined

[travisbot]

This pull request fails (merged 3df9822 into d645ce9).

[travisbot]

This pull request fails (merged c93a0af into d645ce9).

[travisbot]

This pull request passes (merged 4182fb4 into d645ce9).

[coveralls]

Changes Unknown when pulling 4182fb4 on elasticsales:master into * on MongoEngine:master*.