* Allow both both hoidays and append holidays
Match holidays in predict and fit
Add test for append_holiday features; minor fixes
Add column name validation for append_holidays names; allow only one country
Fix bug about holiday year different from input year and also other bugs
Change function description
Add append holiday feature for R
* Add test for R/Pyrhon; fix bugs
* Add metrics for model validation
* Update to reflect comments on Github
* Change all_metrics() implementation to more sophisticated style
* Update metrics functions
* Remove redundant argument
* Use v0.3 files for diagnostics.R and prophet.R
* Use v0.3 file for man/predict.prophet.Rd
* Change the interface and do some refactoring