Currently, (as of 14w08a) this does not appear to be possible. The changelog for 14w07a specifically says that NBT matching works for /testfor and /testforblock. It doesn't appear to work in any other command.
- The commands /testfor, /testforblock and /clear can now test for partial matches of NBT lists
It specifically says those commands, and doesn't mention the @p, @e or @a selectors.
This is very much a currently, as are all snapshot issues. As it is, it doesn't appear to be possible right at this moment.