Use Godep for dependency management and deprecate git submodules

The testdb workbench setup has been changed and moved to a
subdirectory so that the project can appear as a typically packaged Go
project.

Also fix small problems from go vet and go fmt.

Timothée Peignier <timothee.peignier@tryphon.org>
Daniel Farina <daniel@heroku.com>
Add Timothée Peignier <tim@heroku.com> as a contributor
Support 9.4
Support alpha, beta, and development versions
Support PostgreSQL 9.0, 9.1

This only works if the error hooks have been backpatched.

No changes to the fields are known to have been made, so merely
accepting a new version string suffices.