Script should test for required binaries

[aaronsegura]

Per the README:

This script is dependant on the following executables:
`bash` (this is a bash script after all), `wget` or `curl`, `uuidgen`, `grep`, `awk`, `sed`, and `dig`.

The script tests for the existence of wget and curl nicely, but just throws a bash error if any of the other prerequisites are missing. It should test for prerequisites and print a user-friendly error message if any are missing.

PR INCOMING

Thanks!