v1.5.1

• Fix tests on Node <= 0.12.

v1.5.0

• Add tests for async iteration, optional catch binding, import.meta,
  dynamic import, bigint (currently unsupported).
• Add import.meta support. (sourceType: 'module' only)
• Add dynamic import support. (sourceType: 'module' only)
• Fix optional catch binding support in the walker.

v1.4.0

• Upgrade acorn to 5.6, which supports optional catch bindings and other
  new syntax features.
• Set ecmaVersion to 2019 to opt in to optional catch bindings etc.