Do option validation

Currently gluegun doesn't do any option validation so you can invoke with `--any-random-option` and it won't complain. Also it only works with options coming after the positional arguments, which is highly unconventional and unfriendly.

gluegun uses `yargs` under the hood but I can't figure out how to fix this. Based on a quick look at the gluegun source I think it's a fundamental limitation of gluegun. TBH I'm tempted to scrap gluegun because it doesn't seem to add much value to this project.

Start by tracing how the CLI invokes gluegun and how gluegun configures yargs; the issue names no files or tests. Define the intended option-ordering and unknown-option behavior, then verify that random options are rejected and options work before positional arguments without breaking existing commands.

Written by the indexing model from the issue text.