ENH: renderSurfaceFunction now takes lists of surface images.
BUG: Missing 'stop' in renderSurfaceFunction.
ENH: splitData divides data to training and testing sets.
Fixed spacing.
Merge branch 'master' of https://github.com/stnava/ANTsR into bkandel
WIP: simple network plot
BUG: renderSurface not working when funcimg missing; ENH: plotBasicNetwork uses existing rendering window
ENH: Enabled returning row numbers for splitData.
WIP: rendering work