Updated README.md for 2.4.0
Updated README.md for 2.4.0

datastax/cpp-driver,datastax/cpp-driver,mikefero/cpp-driver,hpcc-systems/cpp-driver,hpcc-systems/cpp-driver,mikefero/cpp-driver,hpcc-systems/cpp-driver,mikefero/cpp-driver,mikefero/cpp-driver,flightaware/cpp-driver,flightaware/cpp-driver,datastax/cpp-driver,datastax/cpp-driver,mikefero/cpp-driver,flightaware/cpp-driver,flightaware/cpp-driver,hpcc-systems/cpp-driver