fix: options.customPath doesn't work for windows toaster

[Araxeus]

This is a really simple solution for a weird problem that somehow got through testing:

There is supposedly an option options.customPath. except it would never work if specified in notify() options
because just before we check for this options. - we call options = utils.mapToWin8(options);
which always result in options.customPath = undefined, since its not an allowedToasterFlag (it gets deleted from the options)

TL:DR - utils.mapToWin8(options) delete options.customPath before it can be used

The easy solution is to just save options.customPath before mapToWin8() is called, and use the saved value

[Araxeus]

Had a little woupsie when I "fixed" balloon and notificationcenter which was unnecessary and resulted in superfluous commits, so this PR should probably be squash merged