v2 of valgrind based memory tests

[Austin Clements]

On Mon, 24 Dec 2012, david at tethera.net wrote:
> These obsolete
>       
>       id:1355196820-29734-1-git-send-email-david at tethera.net
>
> I tried to follow the suggestions of 
>
>   id:20121216191121.GH6187 at mit.edu
>
> pretty closely.

LGTM.  In the long run, I wonder if we want to separate the time and
memory tests like this or if some tests would make sense in either mode.