fix(registry): use confd templated config

A regression from #1190 was introduced where the config file used
was the sample that came from dotcloud/docker-registry instead of
using the confd templated config we use today. Updating the file
to upstream's changes with the common layer as well as changing
the reference to the file in the Dockerfile fixes this regression.
Merge pull request #1396 from deis/registry-config-regression

fix(registry): use confd templated config
test(integration): add basic working framework files
test(integration): working versions of auth and keys commands
chore(tests/integration): vendor json library and adjust indentation
test(integration): working integration tests

Also vendored in the gexpect library for tests.
test(integration): add regression tests for two issues

See github issues #1136 and #1239.

Removed example-play as its taking too much time.
Added `curl` test for each test that launches an app.
refactor(tests/integration): move to common tests package