Things to do:
=============

- String: Boundary checking on index and subtring operators
- String: test cases for numerical conversion
- String: Implement String != regex operator
- String: index and rindex methods with String argument

- date: test parser for invalid dates and syntax errors
- date: Parser for stream input
- date: Weekday and week number

- UTC: Convert to and from time_t, struct tm

- Add classes: configuration, Integer, amount