Method the_rest

docopt.cpp:128–134

	}

	std::string the_rest() const {
		if (!*this)
			return {};
		return join(fTokens.begin()+static_cast<std::ptrdiff_t>(fIndex),
			    fTokens.end(),
			    " ");
	}

	std::string pop() {
		return std::move(fTokens.at(fIndex++));