Script to generate secret keys for password reset functionality

Good morning guys, I was wondering about the easiest way for a newcomer to deal with it without add bloated code. This is my initial suggestion, I've tested it on OpenShift and it works like expected, my idea is to add the same script into OpenShift hooks like @fjuma did here (https://github.com/fjuma/openshift-origin-cartridge-aerogear-push/blob/master/bin/install#L22), I think this is the less intrusive option.

For OpenShift maybe we can do something like:

    secret_key=`openssl rand -rand /dev/urandom -hex 64`
    echo "secret_key" > ${OPENSHIFT_AEROGEAR_PUSH_DIR}/env/OPENSHIFT_AEROGEAR_PUSH_SECRET_KEY

This script of course, could be added to the README instead of a *.sh file. Btw let's add or merge @sebastienblanc PR before we merge this one.

Wdyt?