Improve Base.isObject() to only return true for real "vanilla" JS objects.

lib/bootstrap.js

@@ -19,9 +19,6 @@ var Base = new function() { // Bootstrap scope
 		isArray = Array.isArray = Array.isArray || function(obj) {
 			return toString.call(obj) === '[object Array]';
 		},
-		isObject = function(obj) {
-			return toString.call(obj) === '[object Object]';
-		},
 		slice = proto.slice,
 		forEach = proto.forEach || function(iter, bind) {
 			for (var i = 0, l = this.length; i < l; i++)
@@ -325,15 +322,20 @@ var Base = new function() { // Bootstrap scope
 			// Expose some local privates as Base generics.
 			each: each,
 			clone: clone,
+			define: define,
+			describe: describe,
+			iterator: iterator,
+
 			// Base.create does something different from Object.create, it only
 			// works on constructors and uses their prototype.
 			create: function(ctor) {
 				return create(ctor.prototype);
 			},
-			define: define,
-			describe: describe,
-			iterator: iterator,
-			isObject: isObject,
+
+			isObject: function(obj) {
+				return obj !== null && typeof obj === 'object'
+					&& Object.getPrototypeOf(obj) === Object.prototype;
+			},
 
 			check: function(obj) {
 				return !!(obj || obj === 0);