Fix UNIX bash path-setting commands.
Fix UNIX bash path-setting commands.

See discussion in issue #50.

elkingtonmcb/simbody,chrisdembia/simbody,Gjacquenot/simbody,Gjacquenot/simbody,elkingtonmcb/simbody,scamille/simbody,Gjacquenot/simbody,chrisdembia/simbody,elkingtonmcb/simbody,scamille/simbody,simbody/simbody,robojukie/simbody,robojukie/simbody,robojukie/simbody,chrisdembia/simbody,scamille/simbody,simbody/simbody