Ensure tests get coverage too.

Remove cruft surfaced by reporting coverage on test modules.
Remove no-longer-usefule _Response mock.

Use native dicts instead.
Merge pull request #207 from dhermes/indent-four-spaces

Indenting four spaces in all files.
Merge pull request #209 from tseaver/coverage_for_tests

Ensure tests get coverage too.
Making all modules in gcloud package pylint compliant.