Remove notes about datetime.date objects and timezone matching.

Issues #278 and #279 have been filed to address.
Document regression tests, make run_regression fail if environ not set.
Adding support for queries in regression test.

This ports the gcloud-node regression tests for queries
over to gcloud-python.
Making tox regression handle all local and Travis simultaneously.
Making get_dataset() in regression utils use a global.
Merge pull request #281 from dhermes/functional-test-part2

Functional test - Add datastore query tests
Using custom Travis-built wheels when installing.
Making sure the wheels are rebuilt after a change to master.

Other changes
- Fixes the directory that the wheelhouse was in.
- Consolidates the merge check into merge.sh.
- Checks bash code for style with shellcheck.