Restrictions of DEMO version

Demo version is intended for learning Ruby features
and it is very limited comparing with full version.
Art first, it does not proceed MIN and MAX parameters and
uses their default values (68 and 80).
It acceps only required names of initial and result files
(and does not provide output into standard output stream).
So ir has simplified error and parameters analyses
(no HELP or VERSION parameters)
Also, it does not use classes and modules in its implementation.

