Fix class name for Payment in allocation_spec

[wsmoak]

This test is failing on master: https://travis-ci.org/chargify/chargify_api_ares/jobs/128883049

Examining the response, this should be Chargify::Payment not Chargify::Allocation::Payment

[#<Chargify::Allocation:0x007f944d267d28 @attributes={"component_id"=>456, "subscription_id"=>123, "quantity"=>1, "previous_quantity"=>0, "memo"=>"test", "timestamp"=>"2016-05-27 11:45:08 -0400", "proration_upgrade_scheme"=>"prorate-attempt-capture", "proration_downgrade_scheme"=>"no-prorate", "payment"=>#<Chargify::Payment:0x007f944d266e50 @attributes={"amount_in_cents"=>2000, "success"=>true, "memo"=>"Payment for: Prorated component allocation", "id"=>123}, @prefix_options={}, @persisted=false>}, @prefix_options={}, @persisted=true>]

[wsmoak]

This appears to have passed when the original PR for the bulk allocations feature was submitted:
https://travis-ci.org/chargify/chargify_api_ares/builds/98413226

[wsmoak]

Closing. This is not a correct change.

A Chargify::Payment is an external payment, which records something that happened outside Chargify, like receiving a paper check in the mail. See: https://docs.chargify.com/api-payments

This test broke when that resource was introduced in #128 .

The 'Payment' within an 'Allocation' is actually a Chargify::Transaction of type payment. See: https://docs.chargify.com/api-transactions

I am not sure how to get ActiveResource to use the correct class when building up the Allocation object.