This reverts commit 42de44592f. It appears
there might be thread-safety issues as panics have started occuring when
parallism is ramped up. Reverting for now while investigating.
* govendor fetch cloud.google.com/go/bigtable
* Vendor the rest of the stuff.
* Add support for instance_type to google_bigtable_instance.
* Revendored some packages.
* Removed bad packages from vendor.json