Verify command has unclear return codes

[mbrodala]

The codes returned by the verify command are rather odd currently:

1. The path is not a file or does not exist: code 1 (fine)
2. The Phar passed verification: code 1 (should be 0 instead)
3. The Phar failed verification: code 0 (should be at least 1 instead)

The return codes for 2. and 3. do not match usual CLI behavior and should be fixed.