class ExtOptParse

Add grouping to Ruby's `OptionParser`

Example:

p = ExtOptParse.new
p.group(:group1) { p.on("-a", "A") }
p.group(:group2) { p.on("-b", "B") }
p.group(:group1) { p.on("-c", "C") }
puts p.help

  ...
  -b                               B
  -a                               A
  -c                               C
  ...

@see OptionParser