Do not quote source alias.
Print decent error message if package archive does not exist.
Fix init feature.
Merge branch 'source-unquote' into v0.4-wip
Add --debug option.
The command exec is not implemented in EL.

Cannot use Carton options for this command.
Print output and error from carton command on fail.
Merge remote-tracking branch 'origin/print-output-and-error-on-fail' into epl

* origin/print-output-and-error-on-fail:
  Print output and error from carton command on fail.
  The command exec is not implemented in EL.
  Add --debug option.
  Fix init feature.
  Print decent error message if package archive does not exist.
  Do not quote source alias.