ENH: Use BallTree nearest neighbor search
cleanup
Merge pull request #528 from mluessi/compute_nearest_balltree

ENH: Use BallTree nearest neighbor search
FIX: Fixing transform for vertex_to_mni
FIX: Counter imported from collections not from fixes

Closes #532.
Merge pull request #533 from dengemann/fix_counter

FIX: Counter imported from collections not from fixes
update mpl req