Merge pull request #365 from Wachunga/master

Fix bug with _.last(a, n) where n > a.length and add test

underscore.js

@@ -335,7 +335,7 @@
   // Get the last element of an array. Passing **n** will return the last N
   // values in the array. The **guard** check allows it to work with `_.map`.
   _.last = function(array, n, guard) {
-    return (n != null) && !guard ? slice.call(array, array.length - n) : array[array.length - 1];
+    return (n != null) && !guard ? slice.call(array, Math.max(array.length - n, 0)) : array[array.length - 1];
   };
 
   // Returns everything but the first entry of the array. Aliased as `tail`.