enum 1.6
  - fixed some problems exposed by ruby 1.7, thanks to Johan Holmberg.
  - added Enumerable#group to nest.rb.
  - generalized #nest to allow the initial comparison value to be higher
    than subsequent comparison values.

enum 1.5
  - added, in nest.rb, Enumerable#nest, an inverse for Array#flatten.
  - added Enumerable#product (multiplication over an enum, using inject).
  - added size for sums and products (in the set-theoretic sense) of
    enumerables.

enum 1.4
  - compatible with Ruby 1.6.6 (fixes 'no block given (LocalJumpError)')

enum 1.3
  - op.rb: allow product and other ops to be called with a block, as
    a shortcut (see examples).
  - minor documentation and example changes

enum 1.2
  - Added tree.rb, with methods by_depth and by_breadth.
  - Added inject.rb, adapted from Pickaxe book, p.102.

enum 1.1
  - Added cluster.rb, with methods each_cluster and each_with_neighbors.

enum 1.0
  - First public release.
