though this is nothing official and unfortunately I haven't had the time to adjust this to EaselJS 0.6.0 here is a code-completion for SublimeText: http://indiegamr.com/easeljs-codecompletion-for-sublimetext2/ - but be aware, this is no 'intelligent' completion as you might be used to from Java or AS3, but it includes the methods and attributes ect. from 0.5.0
There is also a TypeScript-definition for CreateJS: https://bitbucket.org/drk4/createjs_ts_definitions (unfortunately also only EaselJS 0.5.0) - but TypeScript is a way better choice than pure JS if you want a good/intelligent code-completion. - But maybe you can find something for 0.6.0 for this on the web.
*Edit: This looks like an updated version for TypeScript: https://nuget.org/packages/easeljs.TypeScript.DefinitelyTyped/