Merge pull request #3 from y-ken/rpm_gpg_signature

Addding GPG signature only for unsigned rpms.

Patch by Y.Kentaro. Thanks!!!
Fix indent
Use "while read" instead of "find -exec"

Because dash doesn't have "export -f".
Improve function name

It is a filter command. So "get_" is storange. A command that names
"get_" will extract information by itself.
Fix build error with "-O2"

https://gist.github.com/y-ken/6fd4721b53205631bd49

Reported by Y.Kentaro. Thanks!!!