oduce
 noticeable oscillations in coverage.  offset in (-.5,1) controls the
 spacing of the locations.  Essentially, a positive offset moves the
 locations away from the center of the array and a negative offset moves
 the windows away from the center.  Using a positive offset gives better
 coverage to areas near the borders.

 USAGE
  [masks,keepLocs] = maskGaussians( siz, M, [width], [offset], [show] )
 
 INPUTS
  siz         - dimensions of each mask
  M           - # mask locations along eac