create-project: Skip directory cleanup on errors when using debug (#1267)
create-project: Skip directory cleanup on errors when using debug (#1267)

Previously the newly create project directory was always removed if errors
occurred during any of `create-project`'s install/lint steps, making
debugging hard. Now if the `--debug` option is used cleanup is skipped,
allowing the user to manually try the command that was failing inside
the incomplete project directory.

Fixes #1263.
edmorley/neutrino-dev,mozilla-neutrino/neutrino-dev,edmorley/neutrino-dev,mozilla-neutrino/neutrino-dev