[mlpack] Range search with periodic boundary conditions

[Ryan Curtin]

On Wed, May 13, 2015 at 11:45:17PM +0800, 董理 wrote:
> You guess is correct! Thanks for saving me~

I've made the includes a little more safe and sane in 4741fa4, so that
you can include either cover_tree.hpp or cover_tree/cover_tree.hpp, but
it'll be a few days before I push that to master (I have some other
things to fix first).

-- 
Ryan Curtin    | "And the last thing I would ever do is lie to you."
ryan at ratml.org |   - Marlon