Added new (pwd) command.

Description: (pwd) displays the present working directory.

Example:

    Score manager - example scores

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

        scores - new (new)

    > lmm

    Score manager - material library

        1: example articulation handler
        2: example dynamic handler
        3: example markup inventory
        4: example notes
        5: example numbers
        6: example pitch range inventory
        7: example sargasso measures

        new material - by hand (nmh)
        new material - with manager (nmm)

    > 5

    Score manager - material library - example numbers

        illustration builder - edit (ibe)
        illustration builder - edit & execute (ibex)
        illustration builder - execute (ibx)
        illustration builder - remove (ibrm)
        illustration builder - stub (ibs)

        material definition - boilerplate (mdbp)
        material definition - edit [mde]
        material definition - execute (mdx)
        material definition - execute & edit (mdxe)
        material definition - remove (mdrm)
        material definition - stub (mds)

        output ly - make (lym)

        output material - boilerplate (ombp)
        output material - make (omm)
        output material - remove (omrm)
        output material - view (omv)

        output pdf - make (pdfm)

        stylesheet - edit (sse)
        stylesheet - select (sss)

    > pwd

    /Users/trevorbaca/Documents/abjad/scoremanager/materials/example_numbers

    > q

The (pwd) command is housed in the secondary package menu:

     package - list (ls)
     package - pwd (pwd)
     package - remove (rm)
     package - rename (ren)