CRAN Release 0.4.29

1. Add api.key argument to getSymbols.FRED() and nudge users to register for one if they do not provide an api.key. Thanks to Rob Schumaker (@robschumaker) for the report. #453

2. Improve chartSeries() error message when 'x' has no observations. Thanks to Doug Edmunds (@dougedmunds) for the suggestion. #442