fix(flipper-static): show default warning message on firing in unknown flags (#715)

Summary:
Passing in unknown options along with `flutter-static` now shows the default warning message as part of the API.

## Changelog
show default warning message on firing in unknown flags
Pull Request resolved: https://github.com/facebook/flipper/pull/715

Test Plan: Tested `yarn start` with unknown arguments. Now raises an error.

Reviewed By: mweststrate

Differential Revision: D19389776

Pulled By: passy

fbshipit-source-id: 2f844e38c8be0e4e53b171b98035338226a0a08a

static/index.js

@@ -70,6 +70,7 @@ const argv = yargs
   })
   .version(global.__VERSION__)
   .help()
+  .strict()
   .parse(process.argv.slice(1));
 
 const {config, configPath, flipperDir} = setup(argv);