Removing unneeded String creation

src/pig_latin.rs

@@ -1,16 +1,14 @@
 pub fn pig_latin(string: &str) -> String {
-    // NOTE: does this need to be a String or can we use the &str passed in?
-    let s = String::from(string);
     let mut portion = String::new();
     let mut latinised = String::new();
     let mut starts_with_vowel = false;
     let vowels = ['a', 'e', 'i', 'o', 'u'];
 
-    if s.is_empty() {
-        return s;
+    if string.is_empty() {
+        return latinised;
     }
 
-    let first_character = s.chars().next().unwrap();
+    let first_character = string.chars().next().unwrap();
 
     if vowels.contains(&first_character) {
         portion.push_str("-hay");
@@ -18,7 +16,7 @@ pub fn pig_latin(string: &str) -> String {
     } else {
         portion = format!("-{}ay", &first_character);
     }
-    for (pos, char) in s.char_indices() {
+    for (pos, char) in string.char_indices() {
         if pos == 0 && !starts_with_vowel {
             continue;
         }