Added Gemnasium badge
Add missing tests for Order.get
Only attributes with values should be parametrized
Add Order invoice resources and attributes

- Create Order#invoices
- Create Order::InvoiceCollection
- Create Order::Invoice
- Use DateTime for all dates
Add simple attributes to Order
Add Order#null_custom_fields
Add Order#placed_on using DateTime
Add Order#currency and Order::Currency
Fix broken members list build in Order::InvoiceCollection

I accidentally committed a class with essential code commented out.
Add Order#order_status and Order::Status
Add Order#total_value and Order::Value
Add Order#delivery and Order::DeliveryDetails
Add contact detail resources and integrate with Order

- Add Order::PartyDetails
- Add Order::Contact
- Add Order#parties
Make regexes more idiomatic and readable

- Use === when boolean return value is wanted
- Store regex in a constant
Add missing Order resources