Add the Rational class
Make Rational subclass of Number
Remove few methods
Implement is_canonical()
Polish
Test Rational
Implement integer()
More tests, stricter Rational::is_canonical()
Rational 4/2 now returns an Integer
Test mulrat()
Rename *int to *num in number.h
Add more tests, refactor
Refactor
Refactor
More tests
Implement powrat()