Move security paragraph down
Move security paragraph down

It's not that common and distracts newbies this document actually is for.

hynek/pyopenssl,mitghi/pyopenssl,aalba6675/pyopenssl,r0ro/pyopenssl,reaperhulk/pyopenssl,mitghi/pyopenssl,mhils/pyopenssl,aalba6675/pyopenssl,mhils/pyopenssl,reaperhulk/pyopenssl,pyca/pyopenssl,hynek/pyopenssl,r0ro/pyopenssl