I just forked this project specifically so I could use priorityQueue() and virtually nothing else. It occurs to me that this is a long-term mistake because I'll miss out on future improvements to this function unless I manually import them.

May I suggest splitting async.js into multiple files in a lib sub-directory, to facilitate delivering async's functionality to the browser whilst eschewing unnecessary bytes?

This may be of little benefit for server-side users, but every byte counts in the front-end.

Also, whilst undertaking this pruning, it occurred to me that dependencies between internal and exported methods isn't always clear unless you carefully read the source code. Modularising could assist in making these interdependencies more clear.

What do you think? Should I start a Pull Request for this, or is a bad idea / waste of time?