Removed the ability for stand alone execution of the diffusion tensor data structure unit tests.
Stand alone execution is unnecessary as the command:
$ ./unit_test_runner.py data/test_diff_tensor.py
will run the tests.
Three things have been changed. Firstly the system path modifications have been removed. Secondly
the 'if __name__ == "__main__":' block has been deleted. Finally the 'svn:executable' property has
been removed from the repository.
