switch to sockets api

[lanterndev]

App Engine released a sockets API back in April 2013. Currently still in Preview and still only available to paid apps (as of March 2014).

The sockets API could allow HTTP CONNECT support as well as streaming the response to the client without storing it in memory first.

If the sockets API is ever made available to free apps as well as paid apps, we could make it super easy for censored users to create their own laeproxy instances, which would add a lot more capacity to the network. Some censored users might even be willing and able to pay for their own laeproxy instances in the meantime, so a first pass could just be writing up some docs on how to deploy your own instance, and then make it easy to tell lantern to use it.

Would obsolete #3, #4, #5, and #10.