ip-up script for mac can't work with the default gateway on another PPP link.

use @yayj 's code in https://github.com/fivesheep/chnroutes/issues/2
Merge pull request #1 from layerssss/pppoemac

ip-up script for mac can't work with the default gateway on another PPP ...
add routeros support
add routeros section in README
Merge pull request #2 from layerssss/routeros

Routeros
Merge pull request #1 from GutenYe/master

can I make a pull request to myself? ... YES!!!