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'.
Regression test for pseudo-hierachy via iterator delimiter and prefix.

Fixes #372.
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'.
Delete demo keys, update demos to use same environment vars as regressions.
Fix names exported by '__all__'.
Update docs on running demo to explain environment variables.
Restore unicode literals.

Since we have decided not to support Python 3.2.x, we can avoid the wart.
Merge pull request #383 from tseaver/remove_demo_key

Delete demo keys, update demos to use same environment vars as regressions
Add a comment explaining testing deeper than two levels of pseudo-hierarchy.

Incorporates feedback from @dhermes:
https://github.com/GoogleCloudPlatform/gcloud-python/pull/376#discussion_r20826236
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 #376 from tseaver/372-pseudo_hierarchy_regression_test

Add regression test for pseudo-hierachy via iterator delimiter and prefix.
Merge pull request #374 from tseaver/modernize-prep_for_py3k

Prepare for py3k