[1214][README.md] Add warning about agents incompatibility
[1214][README.md] Add warning about agents incompatibility

Fiware/context.Cygnus,Fiware/data.Cygnus,telefonicaid/fiware-cygnus,Fiware/context.Cygnus,Fiware/data.Cygnus,telefonicaid/fiware-cygnus,Fiware/data.Cygnus,Fiware/context.Cygnus,Fiware/context.Cygnus,telefonicaid/fiware-cygnus,telefonicaid/fiware-cygnus