TODO.md

• Add post about using custom fonts

• Add post about compiling with lyp

• Add install_lilypond / il command:

  desc "install_lilypond VERSION", "Install a version of Lilypond."
  method_option :default, aliases: '-d', type: :boolean, desc: 'Set default Lilypond version'
  def install_lilypond
    $cmd_options = options

    Lyp::System.test_installed_status!
    args.each do |version|
      Lyp::Lilypond.install(version, options)
    end
  end

• Specs for CLI commands.

• Specs for lilypond command.