call stop instead of quit
check that --help throws error
Support passing up to two numerical values as positional arguments

- The values are interpreted as minimum and maximum number of supported positional arguments, ignoring order
- --help option overrides check for positional arguments
passing numeric values is now the default, passing logical a mere compatibility behavior
Merge branch '3-numarg' of https://github.com/krlmlr/optparse into krlmlr-3-numarg
Merge in Kirill's positional improvements, bump version