Add PPA informations to README

I registered twemproxy project on launchpad here: https://launchpad.net/twemproxy
I created a team "twemproxy" to manage it: https://launchpad.net/~twemproxy (I will be happy to add someone from twitter in it)
Code is auto-import from github here: https://code.launchpad.net/~twemproxy/twemproxy/master
Some recipes are building packages daily or by request: https://code.launchpad.net/~twemproxy/+recipe/twemproxy-stable https://code.launchpad.net/~twemproxy/+recipe/twemproxy-daily

I also created a simple `debian` packaging dir: https://code.launchpad.net/~twemproxy/twemproxy/debian

that's all folks :)