Change the serialization and deserialzation functions of
`FunctionStringMap` to use the GzipTarFile. Also change che filename
of the underlying containers accordingly.
This Oython tool will be used to easily work with PTML.
It currently features two subcommands:
* `cat` prints a PTML to the terminal, with color formatting if
possible;
* `strip` will strip a file of the PTML markup;
Giacomo Vercesi