Add the ability to sign gem with X.509
Check the $PROGRAM_NAME before attempting to sign.

I'm not sure how this exactly works, but that's what the guides tell
me to do: http://guides.rubygems.org/security/

It seems like any gem command would match the expression "gem" then
end of string... =/ Sure this will match `gem build`, but won't it
also match `gem install`??
Merge pull request #126 from jish/josh/sign_with_x509

Add the ability to sign gem with X.509