* Update memory requirement description per #326
* Fix R warning with extra regressor; disallow constant extra regressors.
* Fix unit test broken in new pandas
* Fix diagnostics unit tests for new pandas
* Fix copy with extra seasonalities / regressors Py
* Fix copy with extra seasonalities / regressors R
* Fix weekly_start and yearly_start in R plot_components
* Fix plotting in pandas 0.21 by using pydatetime instead of numpy
* Version bump
* Update README for new version
* Fix missing columns in SHF with extra regressor
