Sort disabled messages for test/demo code.
Disable 'import-error' for test/demo code.

The 'six.moves' module (used in demo code) is known to confuse pylint
when used in conjunction with virtualenv.  See:

https://bitbucket.org/logilab/pylint/issue/73/pylint-is-unable-to-import
Disable 'superfluous-parens' for demo code.

The error trips over using 'print(thing)' in Python2, which is legal,
and forward-compatible to Py3k for simple cases.  Rather than introduce
the 'from __future__ import print_function' into the demo, just suppress
the warning.
Selectively apply patches suggested by 'python-modernize --six-unicode'.
PEP8.
Explicitly declare dep. on 'six'.

We were getting it transitively, but better to say we need it.
PEP8.
Remove spurious 'list(foo.items())' wrappers.

They were wrongly introduced by .
No need for 'try: ... except:' when we have 'six'.
Moar no need for 'try: ... except:' when we have 'six'.
Restore unicode literals.

Since we have decided not to support Python 3.2.x, we can avoid the wart.
Drop future import where we don't use its features.

Incorporates feedback from @dhermes:
https://github.com/GoogleCloudPlatform/gcloud-python/pull/374#discussion_r20826711
https://github.com/GoogleCloudPlatform/gcloud-python/pull/374#discussion_r20826736
Merge pull request #374 from tseaver/modernize-prep_for_py3k

Prepare for py3k