Merge pull request #73 from aubreyja/ww3

Ww3
Changed efault branch to master
Update README.md
Update ww_install.pl
Update install_webwork.sh
Update install_prerequisites.sh
Update install_prerequisites.sh
Update install_prerequisites.sh
Update install_prerequisites.sh
Update install_prerequisites.sh
Update install_prerequisites.sh
Update install_prerequisites.sh
Update ww_install.pl
Update install_prerequisites.sh
Update install_prerequisites.sh
Update install_prerequisites.sh
Update install_prerequisites.sh
Update install_prerequisites.sh
Update install_prerequisites.sh
Update install_prerequisites.sh