[BUGFIX] Extract __version__ to safe import module

[shad7]

The trakt/__init__.py references many modules including 3rd party
modules which might not be installed already. The import within the
setup.py results in an ImportError.

fixes #40

[fuzeman]

This will still import the __init__.py file, leading to the ImportError again:

Traceback (most recent call last):
  File "<string>", line 20, in <module>
  File "/tmp/pip-eCKisP-build/setup.py", line 1, in <module>
    from trakt.version import __version__
  File "trakt/__init__.py", line 3, in <module>
    from trakt.client import TraktClient
  File "trakt/client.py", line 1, in <module>
    from trakt.core.configuration import ConfigurationManager
  File "trakt/core/configuration.py", line 1, in <module>
    from trakt.core.context_collection import ContextCollection
  File "trakt/core/context_collection.py", line 4, in <module>
    from six.moves import _thread as thread
ImportError: No module named six.moves

---

cd05732 should complete the fix, will release a new version now.

There is some more details on possible solutions on https://packaging.python.org/en/latest/single_source_version/#single-sourcing-the-version

[shad7]

@fuzeman Thanks!!