Parse arguments

argv.ex

def main(argv) do
    argv
    |> parse_args
    |> process
  end

  def parse_args(argv) do
    parse = OptionParser.parse(argv, switches: [ help:  :boolean],
                                      aliases: [ h:     :help   ])

    case parse do
      { [ help: true ], _, _ }
        -> :help

      { _, [ user, project, count ], _ }
        -> { user, project, String.to_integer(count) }

      { _, [ user, project ], _ }
        -> { user, project, @default_count }

      _ -> :help

    end
  end