if there is no diff print nothing, and exit 2 if a diff is found

[gergnz]

To mimic grep and other *nix tools exit non-zero (2 I picked) if a difference is found. Also print nothing (not even an empty list) if there is no difference.

[coveralls]

Coverage remained the same at 94.753% when pulling c25f76f on gergnz:non-zero-exit into 55e0c43 on stefankoegl:master.

[stefankoegl]

Hi! Thanks for your contribution :) Is there any precedence for returning 2? I'm asking because it seems kind of arbitrary to me.

[gergnz]

Hi @stefankoegl, it was totally arbitrary. I'm happy to take suggestions on a different exit code.

[gergnz]

A colleague of mine showed me this http://tldp.org/LDP/abs/html/filearchiv.html#DIFFERR2. I'll change to a 1 and push.

[coveralls]

Coverage remained the same at 94.753% when pulling 40f76c9 on gergnz:non-zero-exit into 55e0c43 on stefankoegl:master.

[stefankoegl]

Thanks :)