TST: Added cKDTree vs KDTree sparse_distance_matrix consistency check, tweaked radius
BUG: Fixed cKDTree vs KDTree sparse_distance_matrix discrepancy

Fixed improperly set matrix indexes and adjusted distance to be
consistent with KDTree sparse_distance_matrix results
TST: add random seeds and use correct comparisons in spatial.kdtree tests.

Also some PEP8 edits.
BUG: Fixed a few error messages in scipy.spatial.ckdtree

Also reviewed bug-fixes to sparse_distance_matrix by Przemek Porebski
and fixes to tests by Ralf Gommers.
Merge branch 'pr/2602' into master

Reviewed at https://github.com/scipy/scipy/pull/2602