Correct exit codes

[Doxterpepper]

#201

Changing the exit code for ctrl-c to 130 and the code when printing to stdout to 1.

[sharkdp]

Thank you very much!

Could we maybe introduce constants here to avoid those "magic numbers"? Like EXITCODE_ERROR = 1 and EXITCODE_TERMINATED_BY_SIGINT = 130?

[sharkdp]

Thanks!