Fixes issue #3. toString now shows correctly when only using long options.
Made it halting the processing of options send the remaining tokens to the halt handler.

This is needed if you want to support partial parsing of the command line, e.g.

    command --foo --bar=bar subcommand --subcommandfoo footoo --subcommandbar bar

where the command supports several "subcommands" each ith separate options.

here, if you halt the processing when you receive subcommand, the halt callback will
contain the array [ '--subcommandfoo', 'footoo', '--subcommandbar', 'bar' ]
which can be piped into a new instance of optparse.