Add commented-description for ProductLookup module
Refactor ProductLookup to handle batch requests up to 10 products (Amazon limit)

* Add File responsibility description
* Rename load_from_asin to load_product_batch which receives an string with ASINs separated by comma and always return an Array
* Change get_request_object to include :similar_products
* Update file so it can be ran from the command line
Add ASIN to the response and add default price when not present
Merge branch 'master' into refactor_product_lookup
Update Rakefile db:seed to use ProductLookup module

* Update ProductLookup return description
* Handle Amazon edge cases when SimilarProducts has length of 1 (hash instead of an Array)
Merge pull request #15 from ShopIt2Me/refactor_product_lookup

Refactor product lookup