Silex EOL in June 2018

Symfony 團隊認為新版的 Symfony 4 的修改，已經能讓使用者有和 Silex 相同的使用者體驗，於是決定不再繼續維護 Silex：

http://symfony.com/blog/the-end-of-silex

目前 Silex 將在 6 月結束維護 (EOL, End Of Life)：
So, we’ve decided to not support Symfony 4 in Silex, or at least not add the new features added in 3.4. The current stable version of Silex is still maintained for bugs and security issues. But its end of life is set to June 2018.