iOS: Generate .pem file (push certification)

1) Create a dev and production certificate for push notifications
2) Go to the keychain and look for either the dev or production certificate and export both the certificate and the key (at the same time) and save it to the
3) Open a new terminal:

a)
      cd Desktop
      openssl pkcs12 -in pushcert.p12 -out pushcert.pem -nodes -clcerts

b)
      cd Desktop
      rm pushcert.p12