Update fix tray title issue

- Update the fix on tray title when the title is given as an option in `Tray`
item creation (postponing the call to `SetTitle` during `Tray` item init).

- `NSMenuItem setTitle` [should be and] is called always twice to get the
dimensions of the text label right.

- Add automatic tests for `Tray` item.

PS: @rogerwang sorry :wink: I rushed out a little the previous PR