document new es6 features from v8 4.2

[Fishrock123]

Classes under strict, object literals, anything else?

/cc @domenic

[bnoordhuis]

From here:

Classes and object literals are no longer behind a flag.

Rest parameters, computed property names and Unicode escapes ('\u{xxxx}') are new and behind flags. There is a separate flag for Unicode escapes in regular expressions.

[Fishrock123]

Ah right. Thanks @bnoordhuis.

[Fishrock123]

Doh this was meant to be on the website tracker