Rewrite to incorporate 2 element window into the slice

src/lib.rs

@@ -2,15 +2,10 @@ pub fn build_proverb(list: &[&str]) -> String {
     let mut verse = "".to_string();
 
     if !list.is_empty() {
-        let nail = list.first().unwrap();
-        let mut prev = nail;
-
-        for i in 1..list.len() {
-            let next = list.get(i).unwrap();
-            verse.push_str(&format!("For want of a {} the {} was lost.\n", prev, next));
-            prev = next;
+        for item in list.windows(2) {
+            verse.push_str(&format!("For want of a {} the {} was lost.\n", item[0], item[1]));
         }
-        verse.push_str(&format!("And all for the want of a {}.", nail));
+        verse.push_str(&format!("And all for the want of a {}.", list[0]));
     }
 
     verse