Rest API post contracts: url_encoded lists are not recognized as lists

[davalb]

Brief Description:

Operating System (OS and version): Ubuntu 14.04 OpenBazaar version: OpenBazaar Server v0.1 Hardware: not sure...

Reproducible (Always):

Steps to reproduce:

1. send this request to the API: /api/v1/contracts?expiration_date=&metadata_category=physical%20good&title=Wayne%20Smith%20%20-%20Youthman%20Skanking%20%26%239658%3B%20%26%239835%3B&currency_code=EUR&price=14.95&process_time=1&nsfw=false&shipping_origin=GERMANY&ships_to=UNITED_STATES&est_delivery_domestic=2%20Business%20Days&est_delivery_international=7-21%20Business%20Days&terms_conditions=&returns=&shipping_currency_code=EUR&shipping_domestic=6&shipping_international=12&keywords=%5B%27vinyl%27%2C%27reggae%27%5D&category=&condition=New&sku=&images=2a6b1696e0fa473273fd91d9ac75f049f3fedcff&free_shipping=false&moderators=21ea5e64c195816e5f097abab2814cfeec31c749

Observed Behavior: contract has keyword #['vinyl','reggae']

Expected Behavior: The contract should have two keywords: #vinyl and #reggae