Add a note about Disco installation.
Add a note about Disco installation.

This should resolve issue #440.
oldmantaiter/disco,ErikDubbelboer/disco,ErikDubbelboer/disco,oldmantaiter/disco,simudream/disco,seabirdzh/disco,ktkt2009/disco,discoproject/disco,pombredanne/disco,discoproject/disco,mwilliams3/disco,mozilla/disco,mozilla/disco,ErikDubbelboer/disco,oldmantaiter/disco,beni55/disco,ktkt2009/disco,discoproject/disco,ErikDubbelboer/disco,pooya/disco,ktkt2009/disco,pooya/disco,pombredanne/disco,pombredanne/disco,beni55/disco,simudream/disco,mwilliams3/disco,discoproject/disco,oldmantaiter/disco,seabirdzh/disco,simudream/disco,seabirdzh/disco,pombredanne/disco,discoproject/disco,ktkt2009/disco,mozilla/disco,seabirdzh/disco,simudream/disco,pooya/disco,ErikDubbelboer/disco,beni55/disco,beni55/disco,seabirdzh/disco,oldmantaiter/disco,mwilliams3/disco,ktkt2009/disco,pombredanne/disco,mwilliams3/disco,mwilliams3/disco,pooya/disco,mozilla/disco,simudream/disco,beni55/disco