Add weight module support for sort

Dear,

Thanks for this very good module. I use it to send data for an angular.js client. I have to sort data with weight module. I use angular directive to do this (so client side).

I simply add this line in function _contentapi_retrieve() (about line 330 in content_api.module) to send weight with data:

// Send Weight if module exist
    if (module_exists('weight')) $node->weight_weight = $raw_node->weight_weight;

Works great for me.