nsq: 386 arch support

Hello, I install the nsq programming with the guide of http://bitly.github.io/nsq/deployment/installing.html. But I can't pass the testcase.
The log messages is below. Thanks.

```
xuexg@xuexg-pc:~/develop/go/src/github.com/bitly/nsq$ ./test.sh 
testing nsqd
warning: building out-of-date packages:
	github.com/bitly/nsq/nsq
	github.com/bitly/nsq/util
	github.com/bitly/nsq/util/semver
	github.com/bitly/nsq/util/lookupd
	github.com/bitly/nsq/util/pqueue
installing these packages with 'go test -i' will speed future tests.

=== RUN TestPutMessage
--- FAIL: TestPutMessage (0.14 seconds)
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x1 pc=0x8105f5c]

goroutine 7 [running]:
testing.func·004()
	/usr/local/go/src/pkg/testing/testing.go:348 +0x105
sync/atomic.AddUint64()
	/usr/local/go/src/pkg/sync/atomic/asm_386.s:69 +0xc
github.com/bitly/nsq/nsqd.(*Topic).PutMessage(0x18570e70, 0x18588d20, 0x0, 0x0)
	/home/xuexg/develop/go/src/github.com/bitly/nsq/nsqd/topic.go:140 +0x121
github.com/bitly/nsq/nsqd.TestPutMessage(0x1859d720)
```