Added optional parameter to specify a passphrase if one was used when generating the *.p12 file.
Inspiration for the fix from following Ray Wenderlich's tutorial, http://www.raywenderlich.com/3443/apple-push-notification-services-tutorial-part-12 section: "Generating the Certificate Signing Request (CSR)".
Fixed typo
Merge pull request #1 from HomeFree/master

Added optional parameter to specify a passphrase