Add exception handling.

Make sure to exit with non-zero status on every exception
Output formatting

- Suppress output of empty 'Fail' lines on files that didn't have failures.
- spellcheck
Policy for consistent indentation
Better error handling

Don't exit_now! on bad command line, give help.
Raise severity for inconsistent indentation
Long line truncate

Lines with large number of failed lines number list are truncated by default at
60 chars.
Indentation style policy

Either TAB or SPACES policy can be used, overriding by custom styles file.
Setting severity: default and not default

Fix bad severity assignment. All cases work correctly.