Applied TemporaryDirectoryChange to Manager._run().

This means that once control is delegated to a manager, the current working
directory of the system is temporarily changed to the manager's path.

Example:

    Score manager - example scores

        1: Blue Example Score (2013)
        2: Étude Example Score (2013)
        3: Red Example Score (2013)

        scores - new (new)

    > !pwd

    /Users/trevorbaca/Documents/abjad/scoremanager

    > blue

    Blue Example Score (2013)

        build (u)
        distribution (d)
        makers (k)
        materials (m)
        segments (g)
        setup (p)
        stylesheets (y)

    > g

    Blue Example Score (2013) - segments

        1: segment 01
        2: segment 02

        all segments - lilypond file - interpret (lyi)
        all segments - make module - interpret (mmi)
        all segments - pdf - open (pdfo)
        all segments - pdf - version (pdfs)

        segments - new (new)

    > 1

    Blue Example Score (2013) - segments - segment 01

        definition module - edit (dme)
        definition module - edit at top (dmE)

        make module - stub (mms)

    > !pwd

    /Users/trevorbaca/Documents/abjad/scoremanager/scores/blue_example_score/segments/segment_01

    > q