src: don't set non-primitive values on templates

V8 is going to disallow non-primitive values on v8::FunctionTemplate
and v8::ObjectTemplate because those can't be shared across contexts.

Fixes: https://github.com/nodejs/node/issues/6216
PR-URL: https://github.com/nodejs/node/pull/6228


Reviewed-By: Trevor Norris <trev.norris@gmail.com>