[api] Rename assert.length to assert.lengthOf

This change is caused by nodejs/node-v0.x-archive@8c8d518 (sorry!). This commit made
`assert` module behave like `assert.ok` function, thus (since JavaScript
functions have length), `assert.length == assert.ok.length`. Because of
that, assigning `assert.length` wouldn't change anything (function
properties are freezed).

This is a major API break.

Author: mmalecki

lib/assert/macros.js

@@ -110,7 +110,7 @@ assert.isNotEmpty = function (actual, message) {
     }
 };
 
-assert.length = function (actual, expected, message) {
+assert.lengthOf = function (actual, expected, message) {
     if (actual.length !== expected) {
         assert.fail(actual, expected, message || "expected {actual} to have {expected} element(s)", "length", assert.length);
     }

test/assert-test.js

@@ -13,8 +13,8 @@ vows.describe('vows/assert').addBatch({
             assert.match("hello world", /^[a-z]+ [a-z]+$/);
         },
         "`length`": function (assert) {
-            assert.length("hello world", 11);
-            assert.length([1, 2, 3], 3);
+            assert.lengthOf("hello world", 11);
+            assert.lengthOf([1, 2, 3], 3);
         },
         "`isDefined`": function (assert) {
             assert.isDefined(null);

test/vows-test.js

@@ -112,7 +112,7 @@ vows.describe("Vows").addBatch({
                             return this.context.topics.slice(0);
                         },
                         "should pass the topics down": function (topics) {
-                            assert.length(topics, 2);
+                            assert.lengthOf(topics, 2);
                             assert.equal(topics[0], 101);
                             assert.equal(topics[1], 45);
                         }