v0.4

* Bug Fix - Fix a bug that will result in empty submenu when all the
history items were removed.
* Bug Fix - Fix typo.
* Improve - Source optimized.
* Improve - Better way for handling link status notifications.
* Change - New version will display as notification instead of alert.
* Change - Relunch is not required after account linking.
* Change - Remove usage tracking code. (I don't care anymore.)
* Change - Remove donation alert. (I don't care anymore.)
* Change - LLVM 6.0 as default compiler.
* Change - Code-signing process.