Added pixi.js (1.5.3)

cdnjs only had an older version of pixi.js; 1.5.2
Added pixi.dev.js (1.5.3)

cdnjs only had an older version of pixi.js; 1.5.2
Updated package.json for pixi.js 1.5.3
Merge pull request #3458 from thykka/master

pixi.js updated from 1.5.2 to 1.5.3