Return exit code status 1 on errors. #3

Adding failure tests for these commands while I'm at it as well. We
currently only have coverage for the happy path.
Catch ctrl+c's to avoid stacktraces.

No need to show a stack when a user quits during some action.
Add tests for failures in the check and inject stages.
Remove semi colon and correct some indentation
Merge pull request #21 from pearkes/f-status-codes

Status Codes