When sending payments, popular services PayPal and SWIFT allow users to attach private messages that add an explanation about the payment. Before now, bitcoin services haven't supported this feature. However, CoinSpark just launched a tool that works that accomplishes this for bitcoin transactions. They open sourced this tool so that developers can implement the feature in their own applications. These messages, inserted as metadata on the blockchain, give context for the transaction. Users can explain that a transaction is payment for a loan, for instance, or payment for a bet. The message can come in a variety of forms, whether …