Issue #22070: fixed install script

install script works in both travis-ci and ubuntu 12.04
there was a lot of thrashing here; the diff looks worse than it is, unfortunately.

- do not require root to run node-datasource; changed default ports to 8888 and 8443
- use sudo in install script for only the commands that need it
- use default plv8 packages
- use nvm
- to run node/npm as root, see: https://github.com/tjwebb/xtuple/blob/22070-install-script/scripts/install_xtuple.sh#L114

README is updated.