Fix layout issue in skeleton analytics container.
Initial version of the synapse clustering python script.

Takes a skeleton ID or a graph representing it (and the synapses)
and returns data structures representing implicitly the groups of skeleton
nodes, each group being a synapse cluster.
graph.py can now split the skeletons further with synapse clustering.
The edges between circuit elements belonging to the same neuron are not yet implemented.

Signed-off-by: Albert Cardona <sapristi@gmail.com>
Added scipy=0.11.0 to pip-frozen, necessary for synapse clustering.
Reduced operations in graph.py and synapseclustering.py
from 0.33 to 0.29 seconds, and reduced memory footprint.
Most of the operations are in the dijkstra scipy side of things.