Wrote MaterialPackageWrangler.interpret_illustration_lys() tests.

Description: use (lyi) to interpret ALL illustration.ly files contained in any
visible asset.

Example:

    Red Example Score (2013) - materials

       1: instrumentation
       2: magic numbers
       3: pitch range inventory
       4: tempo inventory

          materials - copy (cp)
          materials - new (new)
          materials - remove (rm)
          materials - rename (ren)

    > lyi

    Will interpret ...

     INPUT: /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/pitch_range_inventory/illustration.ly
    OUTPUT: /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/pitch_range_inventory/illustration.pdf

     INPUT: /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/tempo_inventory/illustration.ly
    OUTPUT: /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/tempo_inventory/illustration.pdf

    Ok? y

    GNU LilyPond 2.19.5
    Processing `/Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/pitch_range_inventory/illustration.ly'
    Parsing...
    Interpreting music...
    Preprocessing graphical objects...
    Finding the ideal number of pages...
    Fitting music on 1 page...
    Drawing systems...
    Layout output to `illustration.ps'...
    Converting to `./illustration.pdf'...
    Success: compilation successfully completed
    Interpreted /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/pitch_range_inventory/illustration.ly.

    GNU LilyPond 2.19.5
    Processing `/Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/tempo_inventory/illustration.ly'
    Parsing...
    Interpreting music...
    Preprocessing graphical objects...
    Finding the ideal number of pages...
    Fitting music on 1 page...
    Drawing systems...
    Layout output to `illustration.ps'...
    Converting to `./illustration.pdf'...
    Success: compilation successfully completed
    Interpreted /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/tempo_inventory/illustration.ly.

    >

This means it is now possible to interpret ALL illustration.ly files everywhere
on your system with a single command: (m lyi).