Your GET looks right off the bat. But I need to know exactly what you're throwing across the socket to the server; your full HTTP Request (it should have headers and stuff, identifying your user agent, what you accept, etc..). You look like you're adding in the accept: application/json header, so that's good, but there could be some stuff that you're missing.
Here's what I'm sending with a straight call to my API:
GET https://apikey:password@armstrong-morar5254.myshopify.com/admin/collects/count.json
Accept: application/json
User-Agent: libwww-perl/6.05
Seems like that's all you need; works fine for me. It's possible if your library is adding in extra stuff, you may get a different response. Shopify tends to break easily.