Typed-zmanim

Added
- repr() content for limudim structures

Fixed
- Bug in `jewish_date.back()` failed when wrapping around first Jewish month

Added
- Limudim support for:
- Parsha
- DafYomiBavli
- DafYomiYerushalmi
- DafHashavuaBavli
- MishnaYomis
- PirkeiAvos
- TehillimMonthly
- Kviah function for JewishDate
- Memoization for better performance on common expensive JewishDate methods

Fixed
- Support for python-dateutil pre-2.7.0
- Added Lag B'Omer as significant day / yom tov

Fixed
- Reintroduced future annotations as quoted type
- Fixed bug on optimization branch for large increments/decrements

Added
- Backward support for Python 3.6 (removed future annotations)

Added
- Elevations used in shaos zmanios calculations if use_elevation property is set
- Hanetz and Shkia methods will use the appropriate calculation based on use_elevation setting
- Support Alos and Tzais offset using temporal minutes
- Various Assur Bemelacha related methods for calendar dates using JewishCalendar,
as well as point-in-time using ZmanimCalendar.
- Delayed candle lighting

Added
- README examples
- repr() content for standard classes
- This changelog :)

Fixed
- Package license to reflect LGPLv2.1
- hebrew_calendar module now included in the package
- package includes required dependencies and python version