Include instructions on generating geoip and geoip6 files

nickm said on legacy/trac#10910 (moved):

Also, I would like an improved README.geoip if possible, to explain how the geoip files are generated now. Should I open a new ticket for that?

If we just want to note the commands necessary to generate the files, how about we write them to the header of geoip and geoip6 files, which is what we did before the A1 madness started. For example, here's how the first lines of geoip could look like:

# Last updated based on February 7 2014 Maxmind GeoLite2 Country
# wget http://geolite.maxmind.com/download/geoip/database/GeoLite2-Country.mmdb.gz
# gunzip GeoLite2-Country.mmdb.gz
# python mmdb-convert.py GeoLite2-Country.mmdb
16777216,16777471,AU

Or we could write these commands to a small README.geoip. In this case, is there anything else we'd want to include in this file? The downside, however, would be that README.geoip would only go into master and not into maint-0.2.3 or maint-0.2.4.

Let me know what you prefer, and I'll write a patch.