tile processing needs to happen in the scope of each individual minute, so that we have the context to write the cspp_geo_gglm_input_files attribute correctly.

initial version of input handling where we determine minutes of interest and then work our way back to files

Allow the user to specify a --goes--sector of "meso1" or "meso2". "meso" still defaults to meso1. Functionally this should only affect the output filenames.

Change the realtime flag from -1 to -r. This will allow argparse to parse negative values without extra handholding.

This could be improved by only ignoring warnings in "released" versions so that we still see them when developing.

attempted fix for the 20s end times issue. we might need to revisit and be more explicit in order to handle bad input as well.

add compression to the tiles produced by satpy. also gets us other satpy updates like the static scaling factors. (fixes #14)

add an example usage message and switch to using RawTextHelpFormatter so that the newlines are preserved in our description (#11)