pass in data path as 1st arg
Merge branch 'master' of github.com:jsherrah/alienMarkovNetworks
set nbr edge contribution of non-ab pixels to 0

In ab-swap, they don't matter in the optimisation.
added full energy computation for multi-class labelling.

There was also a bug in the src/snk potential convention.  It's confusing
 because the edge you prefer to cut is associated with the opposite
terminator node, makes sense?
ab swap: only try unique pairs of a and b, since it's symmetric
Merge branch 'master' of github.com:jsherrah/alienMarkovNetworks