added instructions about dependencies for discodex to tutorial
added instructions about dependencies for discodex to tutorial

discoproject/disco,mwilliams3/disco,mozilla/disco,simudream/disco,discoproject/disco,pooya/disco,mozilla/disco,beni55/disco,pavlobaron/disco_playground,simudream/disco,discoproject/disco,scrapinghub/disco,ErikDubbelboer/disco,ktkt2009/disco,pooya/disco,seabirdzh/disco,ktkt2009/disco,simudream/disco,pombredanne/disco,scrapinghub/disco,discoproject/disco,mozilla/disco,pombredanne/disco,oldmantaiter/disco,seabirdzh/disco,mwilliams3/disco,pooya/disco,beni55/disco,mwilliams3/disco,pombredanne/disco,oldmantaiter/disco,ErikDubbelboer/disco,pavlobaron/disco_playground,beni55/disco,oldmantaiter/disco,ErikDubbelboer/disco,ktkt2009/disco,simudream/disco,pavlobaron/disco_playground,ErikDubbelboer/disco,ErikDubbelboer/disco,beni55/disco,pombredanne/disco,seabirdzh/disco,oldmantaiter/disco,pooya/disco,pavlobaron/disco_playground,mwilliams3/disco,beni55/disco,simudream/disco,pombredanne/disco,ktkt2009/disco,seabirdzh/disco,scrapinghub/disco,seabirdzh/disco,oldmantaiter/disco,mwilliams3/disco,mozilla/disco,scrapinghub/disco,discoproject/disco,ktkt2009/disco