4.0.0

Snapshots generated with assertMatchesSnapshot will break when upgrading to this version. The easiest way to upgrade is to ensure your snapshot tests pass, delete your snapshots, upgrade the package, then rerun the tests to generate new snapshots.

• New snapshot formats when using assertMatchesSnapshot: scalars (strings, integers & floats) are serialized to txt files, objects & arrays are serialized to yaml files
• New TextDriver to store snapshots in txt files
• New ObjectDriver to serialize data to YAML and store snapshots in yaml files
• Removed VarDriver