Fixes for mac
Fixes for mac

--max-procs is not supported on Mac xargs, and -P 0 does not work either (requires > 0)

Instead, using cross-platform way to detect cores http://stackoverflow.com/questions/1715580/how-to-discover-number-of-logical-cores-on-mac-os-x

Also sed -i is not working, added ''. See http://stackoverflow.com/questions/7573368/in-place-edits-with-sed-on-os-x

memex-explorer/image_space,memex-explorer/image_space,smadha/image_space,smadha/image_space,smadha/image_space,memex-explorer/image_space,memex-explorer/image_space,smadha/image_space