Option to throw error when parse encounters duplicate keys?

[jcao219]

> parse('{a:1}')
{ a: 1 }
> parse('{a:1,a:2}')
{ a: 2 }

I know that hjson-js is just following the spec, but it would be great to have an option, as an unnoticed duplicate key can cause hidden bugs.

Further discussion, related: https://github.com/zaach/jsonlint/issues/13