--json vs. buffer limits

[mshanemc]

problem: doing a large load with --json produces a buffer overflow depending on the environment (especially CI) since --json writes out all the results.

proposed: use the --concise flag and only return the success count when --json is also present and there are no errors.

Happy to fix and PR if you're good with the proposed solution. Also, this plugin is amazing.

[mshanemc]

#4