Fix install-abjad.sh script

Signed-off-by: George K. Thiruvathukal <gkt@cs.luc.edu>
Just use pip to install Abjad (for now)

Signed-off-by: George K. Thiruvathukal <gkt@cs.luc.edu>
Merge pull request #1 from gkthiruvathukal/master

Changes to support Travis