To avoid possible duplicate browser requests for PaperScript files, support the data-src attribute as well as src.
To avoid possible duplicate browser requests for PaperScript files, support the data-src attribute as well as src.

Closes #749.

iconexperience/paper.js,byte-foundry/paper.js,li0t/paper.js,EskenderDev/paper.js,byte-foundry/paper.js,mcanthony/paper.js,byte-foundry/paper.js,rgordeev/paper.js,nancymark/paper.js,ClaireRutkoske/paper.js,ClaireRutkoske/paper.js,lehni/paper.js,rgordeev/paper.js,li0t/paper.js,ClaireRutkoske/paper.js,lehni/paper.js,proofme/paper.js,proofme/paper.js,proofme/paper.js,mcanthony/paper.js,rgordeev/paper.js,lehni/paper.js,JunaidPaul/paper.js,iconexperience/paper.js,li0t/paper.js,mcanthony/paper.js,JunaidPaul/paper.js,nancymark/paper.js,EskenderDev/paper.js,nancymark/paper.js,iconexperience/paper.js,EskenderDev/paper.js,JunaidPaul/paper.js