tls support

Hey Guys:

I needed TLS support so I could use log-iss to send logs to papertrail over an encrypted channel.  This actually did the trick!  Was kind of surprised how easy this was in the end.

Lemme know what you think. 
I think we can also re-use the cert pool above like so...

```
config.TlsConfig = &tls.Config{RootCAs: cp}
```

At least according to the example in tls.Dial: http://golang.org/pkg/crypto/tls/#Dial