Handling the Gecko +-2.0 Add-On Manager for a post at http://mschade.me/

gistfile1.js

try { // Old addon manager
    let gExtensionManager = Components.classes[
        "@mozilla.org/extensions/manager;1"]
            .getService(Components.interfaces.nsIExtensionManager);
    let version = gExtensionManager.getItemForID(
        "[email protected]").version;
    Charlifter.Lifter.init(version);
} catch(err) { // New addon manager
    Charlifter.Util.log(err);
    Components.utils.import("resource://gre/modules/AddonManager.jsm");
        AddonManager.getAddonByID("[email protected]",
            function(addon) { Charlifter.Lifter.init(addon.version); }
        );
}