See commit list:

- Added first shot at a mixed portfolio
- Added support for dividends
- Drastic refactor of tests to reflect influence of dividends
Cleaning TODOs

- Removed unneeded data from test csvs
- Added test on average yield
- Minor refactor of strategy
Add tests for data

- Clean up data.py
Simplify dividend accrual
Cut down on todos, broke up data module
Updated files for new asset split
Make proper module
Introduce financial date time library
Limited cleanup
Added test. Some minor package refactors.
Made top level module
Refactored to more idiomatic project structure
Moved test to more idomatic layout
Integrate in financial datetime
Cleaning up todos
Porting data handling to pandas
Refactor towards pandas more

- Average dividend period refactored to use pandas
- Yield between refactored to be more elegant