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
+- String: format operator % like in python
+- String: split and join
+- String: assign fstream objects to read and write a file
+- regex: throw an exception when contructing a regex returns an error
- date: test parser for invalid dates and syntax errors
- date: Parser for stream input
-- date: Weekday and week number
+- date: Yearday, Weekday and week number
- UTC: Convert to and from time_t, struct tm
-- Add classes: configuration, Integer, amount
+- Add classes: xml, configuration, amount