Remove unnecessary code

This commit removes some unnecessary code, such as an extra `String`
clone, unnecessary `return` statements, and an inherent `to_string`
function for the `Regex` wrapper.

A double-quote character considered as a string literal by the
compiler was also changed to a single-quote character, this time
considered as a character by the compiler, for some optimization.

Also a newline is added in order to improve code readablitiy.

src/settings/rule/regex_wrapper.rs

@@ -11,10 +11,6 @@ impl Regex {
     pub fn as_str(&self) -> &str {
         self.0.as_str()
     }
-
-    pub fn to_string(&self) -> String {
-        self.0.to_string()
-    }
 }
 
 use std::hash::{Hash, Hasher};