`grid_shape` generalized to handle non-distributed dims.

Removes `distdims` and `ndistdim` attributes of LocalArray.

Testsuite updated and passing.
Cleans up paralleltest_localarray.py.
More refactorings relating to grid_shape.
Use `next()` from six.py
Make Python 3 happy.
Merge branch 'master' into feature/generalize-cart-comm
Merge branch 'master' into feature/generalize-cart-comm
Merge branch 'master' into feature/generalize-cart-comm

Conflicts:
	distarray/local/tests/paralleltest_localarray.py
pep8 cleanup.
Merge branch 'master' into feature/generalize-cart-comm

Conflicts:
	distarray/local/base.py
	distarray/local/localarray.py
	distarray/local/tests/test_base.py
Merge pull request #232 from enthought/feature/generalize-cart-comm

`grid_shape` generalized to handle non-distributed dims.