Add friendly error message if somebody tries to include lib/firepad.js directyl.
Add friendly error message if somebody tries to include lib/firepad.js directyl.

murugespandian/firepad,kofifus/firepad,shadowcodex/firepad-rethinkdb,woutie012006/firepad,STRd6/firepad,kofifus/firepad,STRd6/firepad,abhishekgahlot/firepad,woutie012006/firepad,missive/firepad,Unrestricted-Coding/firepad-rethinkdb,missive/firepad,nagyistoce/firebase-firepad,cben/firepad,nagyistoce/firebase-firepad,gching/firepad,abhishekgahlot/firepad,dipankar08/firepad,murugespandian/firepad,JudeMartin/firepad,STRd6/firepad,gching/firepad,Unrestricted-Coding/firepad-rethinkdb,cben/firepad,cben/firepad,dipankar08/firepad,JudeMartin/firepad,shadowcodex/firepad-rethinkdb,dipankar08/firepad,JudeMartin/firepad