Old problem with laplacian matrix builder throwing ZeroDivisionError - tried to prevent affinity matrix from having rows where off-diagonals sum to 0 as a fix. Fix involves using binary search as a fall-back so that the local_scale vector is > (tolerance) throughout, with tolerance=0.001
Big changes:

Altered the external calls so they need explicit setting of a tmp directory
(default '/tmp' setting removed in most cases). This might lead to some old
calls no longer working.

Altered DistanceMatrix mask, dists and scale to avoid the cases where
RF distances throw a ZeroDivisionError in calculating the graph laplacian
in spectral clustering.
Merge branch 'feature-spectral'