Extract package first to get chromium-args value

Forward extract package code to get **chromium-args** in package.json.
If we do not make this change, arguments such as **--file-descriptor-limit** will not work if it is in the package.json, because these code run before function [ReadChromiumArgs](https://github.com/rogerwang/node-webkit/blob/master/src/nw_package.cc#L404).