Proton does not work with node v6

[richardhodgson]

richard@september:~/projects/proton.js$ node -v
v0.6.15
richard@september:~/projects/proton.js$ node ./lib/proton.js 
The "sys" module is now called "util". It should have a similar interface.

node.js:201
        throw e; // process.nextTick error, or 'error' event on first tick
              ^
Error: No such module
    at Object.<anonymous> (/home/richard/projects/proton.js/lib/proton.js:7:27)
    at Module._compile (module.js:441:26)
    at Object..js (module.js:459:10)
    at Module.load (module.js:348:31)
    at Function._load (module.js:308:12)
    at Array.0 (module.js:479:10)
    at EventEmitter._tickCallback (node.js:192:40)

From https://github.com/joyent/node/wiki/API-changes-between-v0.4-and-v0.6...

process.binding('net') was removed.

We should also update to using the util module rather than sys to get rid of the warning.