The CreatedAt Munger

A simpler, faster mungebit that takes Postgresql CreatedAt statements in the format of YYYY-MM-DD HH:MM:SS.SSSS and convert them into the choice of...
* days since 1970 (default)
* the hour of day (0-23, use mode="hod")
* the day of week (Mon-Sun, use mode="dow")
* the day of month (1-31, use mode="dom")
* the day of year (1-365, use mode="doy")
* the month of year (1-12 corresponding to Jan-Dec, use mode="moy")
* if the output is a holiday (\code{TRUE} or \code{FALSE}, use mode="holiday")
* if the output is a weekend (\code{TRUE} or \code{FALSE}, use mode="weekend")
* if the output is a business day (\code{TRUE} or \code{FALSE}, use mode="bizday")