ArgvParser is a small library for easily handling the basic
needs when using command line arguments.

This small snippet will show how it works.
Assume the arguments are a port and the script is called foo.

  $ foo -p 22 -- ./my.file

or alternatively

  $ foo -p 22 ./my.file

The way to build this with ArgvParser is:

  require 'argv_parser'

  parser = ArgvParser.new
  parser.hook("-p", "-p [port number]", Integer, {:mandatory => true}) do |p,v|
    puts "Opening ssh on port #{v}."
  end
  parser.hook("-ip", "-ip [ip address]", String, {}) do |p,v|
    puts "Trying this ip address #{v}."
  end
  parser.hook("--", "-- [file name], String, {:mandatory => true}) do |p,v|
    puts "Appending on file #{v}"
  end
  parser.parse! ARGV

First off the new instance of the ArgvParser into which we can
hook any series of argument pairs.
  hook is defined as:
    argument short name
    argument long name
    argument type [nil, Array (comma-delimit), Integer, Float, String]
    options :mandatory => boolean
  block takes p as ArgvParser instance and v as value
  a -- hook is a special case which determines a file and, when found at the
  end of the ARGV params, is optional

  parse! is defined as:
    array of arguments

  help is defined as:
    no arguments

If you require a callback for the hooks, you can create a child class
from ArgvParser and access it via p inside the block.

The call order is set by the order you append the hooks.

Calling help will show the regular help, which can be overridden in
a child class.