create a catches decorator to handle exceptions

Signed-off-by: Alfredo Deza <alfredo@deza.pe>
use the new decorator in cli.py's main entry point

Signed-off-by: Alfredo Deza <alfredo@deza.pe>
fix typos

Signed-off-by: Alfredo Deza <alfredo@deza.pe>
add a bit more docs to demonstrate handler usage in the decorator

Signed-off-by: Alfredo Deza <alfredo@deza.pe>
Merge pull request #37 from alfredodeza/5928

No more KeyboardInterrupt/RuntimeError tracebacks!