throw error if loadtest configurations are missing required parameters or otherwise wonky

[ammarm08]

loadtest doesn't provide very useful error messages.

For example:

loadtest -c 8 -n 500 -p $TEST_FILE http://localhost:3000/endpoint

Will give an error of:

Missing URL arg

This is misleading because the problem is really that we are missing a -t application/json as the -p flag requires a data Type to be passed.

Handling this within Quasimodo is a much better user experience. Not to mention, it could've saved me 15 minutes of debugging lol