fix(offer_count): type obj to array

Care, I dont know that ensureArray so before merging check if its coherent with the error

ParsingError: Problem with the value of property `GetLowestPricedOffersForASINResponse`: 
Problem with the value of property `GetLowestPricedOffersForASINResult`: 
Problem with the value of property `Summary`: 
Problem with the value of property `NumberOfOffers`: 
One of the following problems occured: (0) 
Problem with the value of property "OfferCount": 
One of the following problems occured: (0)

Expected a number, but received an array with value 
[{
  "text":58,
  "attr":{"condition":"used","fulfillmentChannel":"Merchant"}
},
{
  "text":1,
  "attr":{"condition":"new","fulfillmentChannel":"Amazon"}
},
{
  "text":6,
  "attr":{"condition":"new","fulfillmentChannel":"Merchant"}
}],

(1) Expected an object, but received an array with value 
[{...}],

(1) Expected an undefined, but received an object with value {"OfferCount":[{"text":58,"attr":{"condition":"used","fulfillmentChannel":"Merchant"}},{"text":1,"attr":{"condition":"new","fulfillmentChannel":"Amazon"}},{"text":6,"attr":{"condition":"new","fulfillmentChannel":"Merchant"}}]

ScaleLeap / amazon-mws-api-sdk

fix(offer_count): type obj to array #376