Add SimpleForm and fix the first step to select options in New Product f...

What I did:
  - I have add SimpleForm which help to generate View, following the guide: https://github.com/nathanvda/cocoon#simpleform
  - I fix issues about the Param name for product_options, not "options"
Now, we could add product with options, but I still get failure to add Variant. I think you should add new model: product_variants, and in ProductVariant modeil, you should have before_filter :create_variant_if_nil to create variant when we enter new Variant name.