Add sanity checking test
Test type coercion for positional args
Fix type coercion for positional args
Verify that Anys are still passed Strs
Beef up coercion tests a bit
Don't coerce types if we don't have to
Make sure Strs don't coerce unless asked to

Unlike MAIN, which will coerce Strs → Int if it feels like it
Verify that exceptions are propagated and not swallowed