Do not capture buildpack output to log, allow streaming

Change-Id: Iee3549af23945bdc2d3f6237a61e54dbf7bd4016
Add vcap_logging dependency to gemspec

Change-Id: I5b24b633da854d0a14b4d7faae8ff7e8f72e8339
Lock down vcap_logging version

Change-Id: I86e885bb913e8113ece10930ed786c7fe1ad82b9