Require Faraday 0.10 for proper nested array encoding

[ob-stripe]

r? @brandur-stripe
cc @stripe/api-libraries

Fixes #576.

Seems difficult to add a test for this as the issue doesn't happen in stripe-ruby itself. Maybe by setting up some sort of echo server? Not sure if worth the trouble, wdyt?

[brandur-stripe]

Nice again OB! I found it a little hard to believe that a problem in decode could be the cause (why would you need to decode parameters during a request?), but I put a breakpoint in there, and yep, it sure is.

This helped me find another problem too. I have a temporary patch that tries to add integer-indexed hash arrays for subscription_items like this:

diff --git a/lib/stripe/invoice.rb b/lib/stripe/invoice.rb
index c865ec2..48d8ef1 100644
--- a/lib/stripe/invoice.rb
+++ b/lib/stripe/invoice.rb
@@ -7,6 +7,10 @@ module Stripe
     OBJECT_NAME = "invoice".freeze
 
     def self.upcoming(params, opts = {})
+      if params[:subscription_items]
+        params[:subscription_items] = Util.array_to_hash(params[:subscription_items])
+      end
+
       resp, opts = request(:get, upcoming_url, params, opts)
       Util.convert_to_stripe_object(resp.data, opts)
     end

Turns out, that code doesn't work! It's nothing to do with any bugs on our end, but that same code in Faraday sees an integer key (like 0) in outgoing parameters and it just throws it out! This is made worse because it doesn't show up in STRIPE_LOG or anything because as far as it knew, we were sending the right thing to our underlying HTTP library! I only caught the problem with Webmock.

Anyway, I'll fix that one separately.