Querystring Nesting support

[inomn]

The same that #67
But:

• with code review fixes, because the original PR is not updated since.
• using yarn (not npm)

Here is original motivation by @klall

When performing a GET request for an individual asset
from the Shopify Admin API I noticed there isn't support for
nested query parameters.

For example performing this request:
GET /admin/themes/#{id}/assets.json?asset[key]=templates/index.liquid&theme_id=828155753
(https://help.shopify.com/api/reference/asset)

results in a query string seen by the server as follows:
{ theme_id: '11949473849',
asset: { key: 'assets/dci_locales.json' } }

However, the library querystring doesn't support nested objects and
therefore the final request URL sent to shopify isn't formed properly.

It works perfectly if I swap out the querystring library with the qs library.