addWaterYear!

Easily add a waterYear column to your dataRetrieval calls to address #246 (closed):

instFlow <- readNWISdata(sites="05114000", service="iv", 
                   parameterCd="00060", 
                   startDate="2014-05-01T00:00Z",endDate="2014-05-01T12:00Z") %>% 
    addWaterYear

• NWIS formatted df, dateTime column name
• NWIS formatted df, Date column name
• WQP formatted df, lots of date/time columns + fix test