deepEqual not Usable on Buffers

Using nodeunit 0.6 on node 0.4.12 (and others), the following test:

```
exports.test = function (test) {
var a = new Buffer([0]), b = new Buffer([0]);
test.deepEqual(a, b);
test.done();
};
```

Fails with:

```
test
✖ test

AssertionError: deepEqual
at Object.deepEqual (/home/smith/nu/node_modules/nodeunit/lib/types.js:83:39)
at Object. (/home/smith/nu/test.js:3:10)
at Object. (/home/smith/nu/node_modules/nodeunit/lib/core.js:233:16)
at /home/smith/nu/node_modules/nodeunit/lib/core.js:233:16
at Object.runTest (/home/smith/nu/node_modules/nodeunit/lib/core.js:69:9)
at /home/smith/nu/node_modules/nodeunit/lib/core.js:115:25
at /home/smith/nu/node_modules/nodeunit/deps/async.js:508:13
at /home/smith/nu/node_modules/nodeunit/deps/async.js:118:13
at /home/smith/nu/node_modules/nodeunit/deps/async.js:134:9
at /home/smith/nu/node_modules/nodeunit/deps/async.js:507:9
```

This test passes with nodeunit 0.4. It would be nice if deepEqual, or some method, worked to compare Buffers.

This is used on https://github.com/cramerdev/gearman-node/blob/master/test/test-packet.js, among other places.

Start at lib/types.js:83, where the failing deepEqual assertion is reported, and reproduce the issue with the Buffer example from the report. Add a regression test for two equal Buffers and verify that deepEqual accepts them while still reporting unequal Buffers correctly.

Written by the indexing model from the issue text.