Can I use localForage instead of localstorage?
What part of code needs to be changed to support localForage?
Your goal is to use IndexedDB or WebSQL, right? Check out the async branch (and #73), which does that already. It uses sticky.js instead of localForage for the adapter, but if that matters to you, it would be trivial to write one in backbone.dualstorage.adapters.coffee.
The async branch has some failing tests related to how promises act in some situations, but it should otherwise work fine. If you think you'd like to address those issues before I get to it, have at it.