Bump to v3.1.0.

string/trim.js

@@ -35,7 +35,7 @@ function trim(string, chars, guard) {
   if (guard ? isIterateeCall(value, chars, guard) : chars == null) {
     return string.slice(trimmedLeftIndex(string), trimmedRightIndex(string) + 1);
   }
-  chars = baseToString(chars);
+  chars = (chars + '');
   return string.slice(charsLeftIndex(string, chars), charsRightIndex(string, chars) + 1);
 }