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

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

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

Added globals software_version, data_level, data_stream, and input_filenames
Added netcdf daily regen
grabs a netcdf file for each day, and goes through all ascii files
netcdf files are created at /mnt/inst-data/regen_netcdf/aoss/tower/YYYY/MM

Mixed up time and time_offset
time now seconds since epoch

Changed netcdf4 file format to netcdf4_CLASSIC
changed strlen from unlimited to 256
added a no-empty flag
made -o flag required

Without -s and -e, it converts each file into a new netcdf file
if -o is used, it converts it itno those output filenames
otherwise, it uses first stamp to name the files
Uh, doesn't do anything about empty .ascii files yet
Will have to ask about that

zlib for compression
chunksize for compression
both called in netcdf4's create variable instance

Only works when -s and -e are specified at the moment
Created draft nc file
might need to change altitude value