### Breaking changes

The default `ecmaVersion` option value is now 7.

A number of internal method signatures changed, so plugins might need
to be updated.

### Bug fixes

The parser now raises errors on duplicated export names.

`arguments` and `eval` can now be used in shorthand properties.

Duplicate parameter names in non-simple argument lists now always
produce an error.

### New features

The `ecmaVersion` option now also accepts year-style version numbers
(2015, etc).

Support for `async`/`await` syntax when `ecmaVersion` is >= 8.

Support for trailing commas in call expressions when `ecmaVersion` is
>= 8.