ledger2beancount: 2.1 -> 2.5
ledger2beancount: 2.1 -> 2.5

Also, move to fetch src off the official `beancount` github org and update
dependencies. I've run this on my ledger file and it seems to work without issue.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs