Adds __version__ to module (PEP396)

Adds a __version__ attribute to the dashi module in accordance with
PEP396, module clients can verify the version, and make assertions about
the version number using distutils (PEP386). setup.py references the
module's version defined in dashi/__init__.py
Merge pull request #2 from lukecampbell/master

Adds __version__ to dashi module (PEP396)