'cron.sh' edited to make a json backup of database after each scrape; then, to update a symbolic reference to the latest backup.
'nginx.conf' now statically serves a reference to the latest json backup.
DRYed up cron.sh file by adding in a couple BASH variables.
Merge pull request #145 from bepetersn/master

cron.sh: make a backup after each scrape; nginx: statically serve latest backup