Don't output \r on SIGINT

[zr40]

The \r character causes the 'Exiting' message to overwrite other output. For example, when used with Foreman, exiting Foreman causes this output:

Exiting1 worker.1      | 

instead of

17:00:01 worker.1      | Exiting

It's not the responsibility of stalker to clean up weird terminal states. Besides, stdout might not even be connected to a terminal.

This patch removes the \r character.