Subcommands don't show 'help' dialog from argparse

[lzkelley]

Need to find a way to get the subcommand parsers to show their own help, when -h/--help is passed after the subcommand name.

e.g.:

• astrocats -h should run the top-level help.
• astrocats -m catalog -h should run catalog-level help.
• astrocats -m catalog import -h should run the import help.