Duck punch `skip` into `Enumerable` because it should have it.

enumerable_skip.rb

module Enumerable
  
  # Duck punch for Enumerable that adds skip() to bypass
  # the first `n` elements of the enumerator.
  # Use skip/take to retrieve a range of values from an enumerable
  # without forcing the values into an array and using [].
  #
  # This is substantially faster for really big collections, but
  # not so much for small ones. ie use at your own risk
  # Also, skip provides superficially the same behaviour as drop, 
  # but it actually doesn't because `drop` returns the remainder 
  # of the collection as an array, instead of as an enumerable.
  #
  # Benchmark.bm do |x|
  #   x.report("  [] 1e3") { (1..1_000).to_a[200..400] }
  #   x.report("skip 1e3") { (1..1_000).skip(199).take(200) }
  #   x.report("drop 1e3") { (1..1_000).drop(199).take(200) }
  #   x.report("  [] 1e9") { (1..1_000_000_000).to_a[200..400] }
  #   x.report("skip 1e9") { (1..1_000_000_000).skip(199).take(200) }
  #   x.report("drop 1e9") { (1..1_000_000_000).drop(199).take(200) }
  # end
  #
  #           user     system      total        real
  #   [] 1e3  0.000000   0.000000   0.000000 (  0.000244)
  # skip 1e3  0.000000   0.000000   0.000000 (  0.000561)
  # drop 1e3  0.000000   0.000000   0.000000 (  0.000037)
  #   [] 1e9 40.890000   4.830000  45.720000 ( 76.255222)
  # skip 1e9  0.010000   0.010000   0.020000 (  0.000922)
  # drop 1e9 29.660000   4.190000  33.850000 ( 36.297854)
  #
  # ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-darwin14]

  def skip n
    original = each

    Enumerator.new do |yielder|
      begin
        1.upto(n).each { original.next }
        while v = original.next
          yielder << v
        end
      rescue StopIteration
      end
    end
  end
end