update test usage comment

Forgot to update the usage parameters when the test was also updated.
update supported node engine

v0.8 is nearing EOL and don't want to take the time to test with v0.6.
remove unused variable

When the octal string checks were removed, forgot to remove the regex
that checked for those and hex values.
add more strict argument parsing

Want to minimize confusion and possible error, so placed a couple more
appropriate checks in place.