Wrote (oo*) tests.

Description: the command lets you open (and subsequently edit) the output.py
files in all visible material packages:

Example:

    Red Example Score (2013) - materials

       1: instrumentation (AE)
       2: magic numbers
       3: pitch range inventory (AE)
       4: tempo inventory (AE)
       5: time signatures

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

    > oo*
    Will open ...
       /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/instrumentation/output.py
       /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/magic_numbers/output.py
       /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/pitch_range_inventory/output.py
       /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/tempo_inventory/output.py
       /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/time_signatures/output.py
    Ok? y
    5 files to edit

    > q