inspect doesn't write delimiting commas after nested containers

[zslayton]

When stepping out of a container, ion beta inspect will print the appropriate closing delimiter. (] for lists, ) for s-expressions, } for structs.) However, if that container is nested, it should also print a delimiting , if the parent container is a list or struct.

This screenshot demonstrates the incorrect behavior:

Reproducing the command here for copy/pasting:

 echo '{foo:[{bar: a}, {bar: b}, {bar: c}]}' | ion dump --format binary | cargo run -- beta inspect

This isn't currently trivial to fix. Ideally, the reader would expose a method that allows applications to query for its current context. Something like:

fn parent_type(&self) -> Option<IonType>;

that would return None at the top level and Some(container_type) at any other depth. Absent such an API, the application would need to track the reader's traversal manually.

[zslayton]

Fixed in PR #28.