ecomm fixes: use price instead of cost_price. Fixing taxon locator to be more flexible.

Also added :throws_exception => false to the MC API call
Although this doesn't work on the current MC gem master
mailchimp/mailchimp-gem/pull/30 adds this functionality in
Fixing ecomm date formatting bug

V2.0 of the docs states that order_date must in the format 2012-12-30
Fixing failing specs