load-data.py should exit if a bash command returns a non-zero error code.

Change-Id: I2f732a276a42d2697fa55bce0f18ac89e9a6f0a1
Reviewed-on: http://gerrit.ent.cloudera.com:8080/1397
Reviewed-by: Lenni Kuff <lskuff@cloudera.com>
Tested-by: jenkins
Add simple example scanner to illustrate how to write a custom scanner.