+ :_pkgbuild_to_yaml_with_check. ship :install script

* New function :*_with_check will use Ruby/YAML to check the syntax of
  the YAML output provided by :pkgbuild_to_yaml

* The contents of :install script will be shipped with YAML output
* FIXME: Unable to detect :install script of sub-package
* FIXME: Unable to detect sub-packages information
Return if we are not be able to update :_func variable