FreeBSD compatible

Detect the OS and use gtimeout from sysutils/coreutils
FreeBSD + extra chacha20 repo

I've found another repository which offers 1.0.2 with chacha20
I've added some extra instructions for FreeBSD users
OpenSSL 1.0.2 is not a requirement

Back when egrep wasn't working, I tried to fix various things and 1.0.2 was allowing the script to go further without breaking. After having installed a more recent version of GNU grep, things were back to normal and 1.0.1 works fine
Merge pull request #1 from oparoz/patch-1

Patch 1