Overriding standard in/out/error in Subcommand
Overriding standard in/out/error in Subcommand

`Ey::Core::Cli::Subcommand#setup` now sets the global
std(in|out|err) to the objects received at app initialization.

Effectively, this just makes testing way easier, but also
guarantees that we use known IO interfaces.

engineyard/core-client-rb