Documented functions relating to apparent temperature.
Also made some minor validity checks inside HeatIndex and WindChill functions to ensure valid values are returned.
Moved ReduceWeather to dataframe_processing.R
Reordered functions in dataframe_processing.R to be alphabetical.
Created HumidexDiff and WindChillDiff functions.
Optimized the evaluation of the functions a bit using na.rm = TRUE with min(...) and max(...) functions rather than goofy sort(...) thing I was doing.
Simplified some of the pre-processing functions.
Offloaded the responsibility for getting hour, month, and weekend as strings to the SQL query.
Also initialized column types more intelligently with read.csv such that FixDatatypes is no longer needed and InitReadingsDataFrame replaces InitAggregateReadings function.