Acceptance tests for app usage event

Verify app usage events from application lifecycle:

* STARTED
* BUILDPACK_SET
* STOPPED

[#69196650]
Merge pull request #21 from sykesm/app-usage-events

Acceptance tests for new app usage event 'BUILDPACK_SET' that gets triggered on staging completion.
Updated to use latest cf-test-helpers

[#71337862]

Signed-off-by: Michael Fraenkel <fraenkel@us.ibm.com>
Added expectation that StdErr is empty after a Curl

Signed-off-by: Michael Fraenkel <fraenkel@us.ibm.com>
Updated to use Wait+Expect instead fo Eventually

Signed-off-by: Michael Fraenkel <fraenkel@us.ibm.com>
Update buildpack test to reflect new error message

[#68122384]
Merge pull request #23 from sykesm/detect-error-message

Update buildpack test to reflect new error message
Add test to verify ruby version used for staging

[#71367862]

Signed-off-by: Michael Fraenkel <fraenkel@us.ibm.com>
Merge branch 'master' into diego
bin/test does not run diego