Refactor scheme/Lilypond API (#61)

- Deprecate `\require`, `\pinclude` et al commands. They still work, but
  will produce a warning when verbose option is used.
- Introduce new commands to replace the old commands:
  - `lyp-require`: load a package
  - `lyp-load`: load a file
  - `lyp-include`: load a file only once
- Richer, easier to use `lyp-include` commands accept:
  - directory for loading all files in directory: `\lyp-include utils`
  - filename pattern with wildcard: `\lyp-include "lib/*.ly"`
  - multiple file references: `\lyp-include #'(stave1 stave2)`
- Cleanup and refactor scheme definitions.

.gitignore

@@ -4,4 +4,7 @@ dist
 *.pdf
 *.ps
 *.png
-*.svg
+*.svg
+test.ly
+spec/package_setups/tmp
+spec/lilypond_setups/tmp

TODO.md

@@ -1,14 +1,22 @@
-- Specs for CLI commands.
+- Add post about using custom fonts
+- Add post about compiling with lyp
 
-- Specs for lilypond command.
+- Add `install_lilypond` / `il` command:
 
-- rename require, pinclude, pincludeOnce etc:
+```ruby
+  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
 
-```lilypond
-\req "blah"
-\incl "blah.ly"
-\inclOnce "blah.ly"
-\condIncl #(eq? edition 'urtext) "urtext_tweaks.ly"
-\condInclOnce #(eq? edition 'urtext) "urtext_tweaks.ly"
+    Lyp::System.test_installed_status!
+    args.each do |version|
+      Lyp::Lilypond.install(version, options)
+    end
+  end
 ```
 
+- Specs for CLI commands.
+
+- Specs for lilypond command.
+

docs/news.md

@@ -20,6 +20,10 @@ $ lilypond mymusic.ly
 
 _2018/2/5_
 
+<div>
+  <script src="https://asciinema.org/a/123683.js" id="asciicast-123683" async></script>
+</div>
+
 It's been a year since I last worked on lyp. Fortunately, some people still care about it and have brought some [issues](https://github.com/noteflakes/lyp/issues) to my attention. I've been able to help some of them and have just put out a new release. Also, in the last few days the old Lilypond binaries download link has stopped working. I've updated lyp to download from the new location (on the lilypond.org website). So you should update your lyp installation to the latest version - 1.3.8. Here are some of the changes since 2017:
 
 - Fix Lilypond installation link (the  http://download.linuxaudio.org/lilypond links don't work anymore).