Issue #79. Correctly setting 'this' in '_.wrap'

test/functions.js

@@ -96,6 +96,11 @@ $(document).ready(function() {
     var greet = function(name){ return "hi: " + name; };
     var backwards = _.wrap(greet, function(func, name){ return func(name) + ' ' + name.split('').reverse().join(''); });
     equals(backwards('moe'), 'hi: moe eom', 'wrapped the saluation function');
+
+    var inner = function(){ return "Hello "; };
+    var obj   = {name : "Moe"};
+    obj.hi    = _.wrap(inner, function(fn){ return fn() + this.name; });
+    equals(obj.hi(), "Hello Moe");
   });
 
   test("functions: compose", function() {

underscore.js

@@ -469,7 +469,7 @@
   _.wrap = function(func, wrapper) {
     return function() {
       var args = [func].concat(slice.call(arguments));
-      return wrapper.apply(wrapper, args);
+      return wrapper.apply(this, args);
     };
   };