Added logging around the returned values for `remaining`.

I changed:

```go
remaining[state.Remaining] = true
```
to
```go
log.Printf("got %d remaining", state.Remaining)
remaining[state.Remaining] = true
```

and things get weird:

```bash
=== RUN TestThreadSafeAdd
2014/03/31 14:15:29 got 99 remaining
2014/03/31 14:15:29 got 88 remaining
2014/03/31 14:15:29 got 89 remaining
2014/03/31 14:15:29 got 90 remaining
2014/03/31 14:15:29 got 91 remaining
2014/03/31 14:15:29 got 92 remaining
2014/03/31 14:15:29 got 93 remaining
2014/03/31 14:15:29 got 94 remaining
2014/03/31 14:15:29 got 95 remaining
2014/03/31 14:15:29 got 96 remaining
2014/03/31 14:15:29 got 97 remaining
2014/03/31 14:15:29 got 98 remaining
2014/03/31 14:15:29 got 73 remaining
2014/03/31 14:15:29 got 74 remaining
2014/03/31 14:15:29 got 75 remaining
2014/03/31 14:15:29 got 76 remaining
2014/03/31 14:15:29 got 77 remaining
2014/03/31 14:15:29 got 78 remaining
2014/03/31 14:15:29 got 79 remaining
2014/03/31 14:15:29 got 80 remaining
2014/03/31 14:15:29 got 81 remaining
2014/03/31 14:15:29 got 82 remaining
2014/03/31 14:15:29 got 83 remaining
2014/03/31 14:15:29 got 84 remaining
2014/03/31 14:15:29 got 85 remaining
2014/03/31 14:15:29 got 86 remaining
2014/03/31 14:15:29 got 87 remaining
2014/03/31 14:15:29 got 68 remaining
2014/03/31 14:15:29 got 69 remaining
2014/03/31 14:15:29 got 70 remaining
2014/03/31 14:15:29 got 71 remaining
2014/03/31 14:15:29 got 72 remaining
2014/03/31 14:15:29 got 37 remaining
2014/03/31 14:15:29 got 38 remaining
2014/03/31 14:15:29 got 39 remaining
2014/03/31 14:15:29 got 40 remaining
2014/03/31 14:15:29 got 41 remaining
2014/03/31 14:15:29 got 42 remaining
2014/03/31 14:15:29 got 43 remaining
2014/03/31 14:15:29 got 44 remaining
2014/03/31 14:15:29 got 45 remaining
2014/03/31 14:15:29 got 46 remaining
2014/03/31 14:15:29 got 47 remaining
2014/03/31 14:15:29 got 48 remaining
2014/03/31 14:15:29 got 49 remaining
2014/03/31 14:15:29 got 50 remaining
2014/03/31 14:15:29 got 51 remaining
2014/03/31 14:15:29 got 52 remaining
2014/03/31 14:15:29 got 53 remaining
2014/03/31 14:15:29 got 54 remaining
2014/03/31 14:15:29 got 55 remaining
2014/03/31 14:15:29 got 56 remaining
2014/03/31 14:15:29 got 57 remaining
2014/03/31 14:15:29 got 58 remaining
2014/03/31 14:15:29 got 59 remaining
2014/03/31 14:15:29 got 60 remaining
2014/03/31 14:15:29 got 61 remaining
2014/03/31 14:15:29 got 62 remaining
2014/03/31 14:15:29 got 63 remaining
2014/03/31 14:15:29 got 64 remaining
2014/03/31 14:15:29 got 65 remaining
2014/03/31 14:15:29 got 66 remaining
2014/03/31 14:15:29 got 67 remaining
2014/03/31 14:15:29 got 34 remaining
2014/03/31 14:15:29 got 35 remaining
2014/03/31 14:15:29 got 36 remaining
2014/03/31 14:15:29 got 33 remaining
2014/03/31 14:15:29 got 32 remaining
2014/03/31 14:15:29 got 31 remaining
2014/03/31 14:15:29 got 30 remaining
2014/03/31 14:15:29 got 27 remaining
2014/03/31 14:15:29 got 28 remaining
2014/03/31 14:15:29 got 29 remaining
2014/03/31 14:15:29 got 14 remaining
2014/03/31 14:15:29 got 15 remaining
2014/03/31 14:15:29 got 16 remaining
2014/03/31 14:15:29 got 17 remaining
2014/03/31 14:15:29 got 18 remaining
2014/03/31 14:15:29 got 19 remaining
2014/03/31 14:15:29 got 20 remaining
2014/03/31 14:15:29 got 21 remaining
2014/03/31 14:15:29 got 22 remaining
2014/03/31 14:15:29 got 23 remaining
2014/03/31 14:15:29 got 24 remaining
2014/03/31 14:15:29 got 25 remaining
2014/03/31 14:15:29 got 26 remaining
2014/03/31 14:15:29 got 8 remaining
2014/03/31 14:15:29 got 9 remaining
2014/03/31 14:15:29 got 10 remaining
2014/03/31 14:15:29 got 11 remaining
2014/03/31 14:15:29 got 12 remaining
2014/03/31 14:15:29 got 13 remaining
2014/03/31 14:15:29 got 18446744073709551615 remaining
2014/03/31 14:15:29 got 0 remaining
2014/03/31 14:15:29 got 1 remaining
2014/03/31 14:15:29 got 2 remaining
2014/03/31 14:15:29 got 3 remaining
2014/03/31 14:15:29 got 4 remaining
2014/03/31 14:15:29 got 5 remaining
2014/03/31 14:15:29 got 6 remaining
2014/03/31 14:15:29 got 7 remaining
--- FAIL: TestThreadSafeAdd (0.02 seconds)
	test.go:103: Did not observe correct bucket states. Saw 101 distinct remaining values instead of 100: ...
```

Looks like we never return 100 for remaining, so it's unclear on how that gets into the map. The states we're returning look good - since remaining et. al. are unsigned ints, the -1 that we would expect to see turns into 18446744073709551615.