Includes addition of 'calendar' attribute to time variable in netcdf

base_time is epoch seconds
time_offset is seconds from base_time
time is hours from midnight

Includes fixes and clean up for specifying multiple files versus
a single input file.

Properly calculate wind gust
Properly assign QC flags
Tons of style changes and better performant array operations

If dewpoint is missing from netcdf files, the script uses rel_hum and
air_temp data to recreate dewpoint data

--daily was calculating min and max of temperature and dewpoint
plot wrong by not considering dewpoint at all - that has now
been fixed

Title was a bit too big
changed it to 13

creates aoss tower quicklooks

1 min files now have datastream nc-1d-1m
monthly files now have datastream nc-1mo-1m

If dates don't line up exactly at the minute mark, the frame gets filled with np.nans
now frame takes closest record that is < than the minute mark and sets
that record into the file

Some variables weren't in frame and qc were marking them as 'good'
Now they are marked as missing as desired

need to reorganize headers in the future

schema contains valid_min and max values
level_b1's nc.py now implements those values into the netCDF header:

every five seconds, a new rolling 2 minute average is calculated
every minute, only 1 average is stored in the file's memory

averages now start at future minute - 1 to future minute

averages all vars now except wind_speed and wind_direction
Haven't added gust yet

If -s is specified alone, script creates file from -s to end of the day
argparse now allows format YYYY-MM-DD

Got rid of the --no-empty flag
If empty ASCII file, doesn't create a nc file
If all ASCII files are empty, raise IO ERROR