class String
  #
  # String#word_slice
  #
  # As original String::slice but tries to cut whole words instead of characters.
  # How many extra extra chars that should be allowed is specified by the second argument.
  #
  # "A long article that needs a nice cut".slice(1..10)   # => "A long arti"
  #
  # "A long article that needs a nice cut".word_slice(1..10)   # => "A long article"
  #
  def word_slice(range, max_extra_chars = 20)
    offset = range.max + 1
    string = self.slice(range)

    if self[offset,max_extra_chars] =~ /(^[a-zA-Z0-9]+)/
      string << $1
    end

    string
  end
end