Fix some errors and warnings when enabling/disabling features (#821)

* Fix E&Ws when enabling features

* `share_clipboard` feature can be disabled more cleanly

* `notify` feature can be disabled more cleanly

src/utils.rs

@@ -1,3 +1,5 @@
+#![allow(dead_code)]
+
 /// Returns a human readable String of a Duration
 ///
 /// Example: `3h 12m 53s`