CLI stat command

Looks like: 

```
$ doss stat 2 4
2: 
	Created:	Wed Jul 17 16:08:16 EST 2013
	Modified:	Wed Jul 17 16:08:16 EST 2013
	Accessed:	Wed Jul 17 16:08:16 EST 2013
	Key:		(dev=1000002,ino=8382459)
	Size:		24.1 KB

4: 
	Created:	Wed Jul 17 16:08:16 EST 2013
	Modified:	Wed Jul 17 16:08:16 EST 2013
	Accessed:	Wed Jul 17 16:08:16 EST 2013
	Key:		(dev=1000002,ino=8382463)
	Size:		94.3 KB
```

It also accepts a -b option for displaying just the number of bytes.  There is the potential for many more little options as you think of them.

The difference between this and the last pull request (nla/doss/pull/36) is that this one is called `stat`, and that I have created a new Status interface for getting things like dates, etc.  Blob implementations must implement that stuff themselves (I figure they're more likely to know about how to get those sorts of things).

I'm also still iffy about if we need modified and access dates.