Print out stack traces when Aphlict server dies

Summary: Printing out `err` is less informative than `err.stack`, which has the message, type, //and// a trace.

Test Plan:
Faked an exception, then:

```
$ sudo ./bin/aphlict debug
Starting Aphlict server in foreground...
Launching server:

    $ 'node' '/INSECURE/devtools/phabricator/src/applications/aphlict/management/../../../../support/aphlict/server/aphlict_server.js' --port='22280' --admin='22281' --host='localhost'

[Wed Jun 11 2014 10:20:39 GMT-0700 (PDT)]
<<< UNCAUGHT EXCEPTION! >>>
Error: Example Exception
    at Object.<anonymous> (/INSECURE/devtools/phabricator/support/aphlict/server/aphlict_server.js:73:7)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)
    at startup (node.js:119:16)
    at node.js:901:3
>>> Server exited!
```

Reviewers: joshuaspence

Reviewed By: joshuaspence

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D9481