[MRG] Nearest neighbor radius query should include points in the boundary.

Noticed that although `kd_tree` and `ball_tree` algorithms return points in the boundaries, the `brute` method does not. Included a fix for `brute` and added a toy testcase to check the consistency between the algorithms for this edgecase.
Can you please install [pep8](https://pypi.python.org/pypi/pep8), run it on the files impacted by this PR and fix the warnings related only to your change.