Remove cyclic import from ignored for tests.
Reducing repeated pylint configs by defining test configs as a delta.

Uses ConfigParser to append modifications onto base file and
writes a new config file (which is gitignore-ed) before running
pylint.
Putting pylint additions for tests into run_pylint.
Implementing remaining datastore regression tests from gcloud-node.
Merge pull request #302 from dhermes/remove-cyclic-twice

Remove cyclic import from ignored for tests.
Uses pre-built wheels when pip installing from tox.

In addition:
- Creates script scripts/update_wheels_project.sh to kick off a new
  build when merging to master (outside of a PR).
- Moves update_docs into a larger group of merge scripts
  that happen when merging to master.
Merge pull request #307 from dhermes/finish-datastore-regression

Implementing remaining datastore regression tests from gcloud-node.
Merge pull request #308 from dhermes/speed-up-build-stage-two

Uses pre-built wheels when pip installing from tox.
Refactoring duplicate code between storage.key and storage.bucket.