Update README to new iprange version

[AndreasHD23]

Thanks again for this great solution. Works like a charm.

You might want to update the README to the "new" (2018) 1.0.4 version of iprange.
Version 1.0.3 is not in the pool anymore.

curl -O http://http.us.debian.org/debian/pool/main/i/iprange/iprange_1.0.4+ds-2_mips.deb
curl -O http://http.us.debian.org/debian/pool/main/i/iprange/iprange_1.0.4+ds-2_mipsel.deb

I am using 1.0.4+ds-2_mipsel on an ERX SFP - nothing broken.

Cheers