Implemented the 'fraction_count'/'fcount' binning method in get_bins():

  Returns an array of bins, each bin containing the sum of the fractions
  of features overlapping that bin.  A feature fully inside a bin will
  contribute 1 to the sum while a feature spanning exactly three bins
  (from the very start of the first to the very end of the third) will
  contribute 1/3 to the sum of each bin.