Consider making the API consistent for fetch_stock and fetch_tracking_numbers

[kevinhughes27]

Currently fetch_stock takes a hash in which it expects :sku for a specific sku or if nothing is sent we expect all the skus to be returned to us. Other options may be sent in this hash and they will be included in the request.

fetch_tracking_numbers / data however takes order_ids and then an options hash with other options that will be sent in the request. We should make these two methods take consistent args, either both only a hash or hash for extra args and a specific var for the main data.

[wvanbergen]

We could tackle this as part of the major release (see #49). Is it worth the time investment?

@jnormore @csaunders @kmcphillips

[csaunders]

It's a major API version change so this is kinda the best opportunity to make that change.

Might break some bits of Shopify though, so might get in the way a bit :(

[kevinhughes27]

it won't be too bad to fix in Shopify - I can help out if you'd like.

I think we should probably do this now.

[wvanbergen]

@pickle27 Let's sit down next week to tackle this.