chore: minor cleanup before 0.4.0 release

* remove `freq` from build_trading_timeline
* fix coverage support for shippable
* fix coveralls support for drone.io and others
* fix zipline version dependent tests
* more comments in code
* bump latest packages version
Merge branch 'release/v0.4.0' into develop
chore: hotfixes post 0.4.0, before insights release

* Use Pypi pandas package (0.13.1)
* Add `intuition.data.remote.fill_stock_metadata()` from insights
* Clean makefiles
* Clean scripts/ and config/
* `portfolio._optimizer_parameters` becomes `portfolio.properties` and there are no longer `parameter` and `date` args in `optimize()` as they already are portfolio attributes
* Remove TradingAlgorithm.days and add elapsed_time property instead
* Check code with pep8 instead of flake8
* Bump zipline version 0.6.1
* TradingAlgorithm.identity set in the constructor
* properties algorithms argument optional