Minimal Accounting Library in Python

The core of the library in under 350 lines of code, and it enables to create a chart of accounts, open a ledger, and post entries to ledger, as well as to close ledger properly at accounting period end.

The resulting reports are income statment and balance sheet. Trial balance can be shown at any time.

Best effort made to document library usage in an end-to-end example in README - needs just Chart, Book and Entry classes to perform. List of simplifications and assumptions used also in README.