Add initializer for top-level '_gcloud_vendor' package.
Don't run pep8/pylint on vendored-in sources.
Vendor in 'apitools/base/py' and parents.

Pulled from e5a5c36e24926310712d20b93b4cdd02424a81f5.
Rip out namsepace package support and convenience imports.
Rip out non-transport-related modules.
Fix up imports.
Merge pull request #400 from tseaver/334-vendor-apitools-subset-redux

#334: vendor-in apitools subset