Typings show tag as optional but check has a guard against null tags

[jhendershott]

When running eyes via typescript you're able to call the method

eyes.checkWindow() and this is valid because tag and matchTimeout are both optional
checkWindow(tag?: string, matchTimeout?: number): Promise;

However when you run you throw a very curious error that "Name" isn't set.

This appears to be due to the guard in Eyes.js
ArgumentGuard.notNullOrEmpty(name, "Name");

Which means that this isn't actually an optional parameter in practice.

Options are to remove ? from tag
jhendershott#1

or remove the guard.

also. it seems like having tag and name separate is very confusing especially if the guard is against 'NAME' and that should likely be updated through out the library