Add support for query params in orders

[abunashir]

Digicert supports to pass query params in the listing interfaces, we already had that one implemented in the all action, but it was not documented.

This commit adds the necessary test cases and document this to the readme, we now can use this to retrieve filtered orders.

Digicert::Order.all(limit: 20, offset: 0, sort: 'date_created')

Reference: Issue #100

[abunashir]

The sort by status responds with an error in some use case scenario but apart from that everything else seems to be working fine. @ronaldtse could you please double check with them and see if something we need to do on our end?

Note: { sort: '-status' } or { sort: '+status' } works fine but not with { sort: 'status' }

[ronaldtse]

@abunashir apologies I didn't catch that comment! I've sent an email to Digicert (and CC'ed) you to see what we can do. Thanks!