Changes in version 0.1.2

- Exported `is_valid_day_basis()` and `is_valid_bdc()` (#5)

Changes in version 0.1.1

- Fixed error when subsetting a `JointCalendar` with a logical vector (#3)
- Removed unnecessary dependency on stats package

Changes in version 0.1.0

- Initial release
- Introduces `Calendar` classes (S3) and associated convenience constructors for
key locales
- Introduces `is_good()`, `adjust()`, `shift()` and  `generate_schedule()` as
key calendar related methods
- Introduces `year_frac()` function for time length calculations.