CentOS stemcell has users

Signed-off-by: Tony Hansmann <thansmann@pivotallabs.com>
Skip plugdev group for vcap user when not on Ubuntu

Signed-off-by: Tony Hansmann <thansmann@pivotallabs.com>
Reduce duplication in ci stemcell tasks
Remove unused method
Use options hash to inject dependencies into Build
Gather knowledge about upload & download adapters
Avoid Travis killing our integration specs for spinning up too many processes

Signed-off-by: Jeffrey Peckham <peckham@pivotallabs.com>
Fixed title in readme