0.3

• Add get_field and get_fields methods to VirtualModel meta class (smark-1)
• Add dedicated DoesNotExist and MultipleObjectsReturned exceptions on VirtualModel
• Implement equality on VirtualModel based on ID
• Make properties start and stop available in addition to offset and limit
• Short-circuit queries if running on an empty slice
• Fix: When retrieving by index, use a single-item slice instead of running the full query