v2.20.0

Changes

• #440 override add_contact to handle different API endpoint (@hegedus)
• #483 Add discount_amount attribute for invoice line item (@jasonheecs)
• #485 Update cell parser regex (@bertiecroll)
• #488 Add Batch Payment model (@jono-booth)

Bug fixes

• Make sure we can convert to BigDecimal with discount_amount (@jasonheecs)

Docs

• #491 Add example for fetching ProfitAndLoss using date range (@dcrtantuco)
• #487 Document how to provide a private key directly (@matt17r)
• #476 Update comment about nonce being used (@austinmckinley)