Add support for saving HostNames to PaperTrail

Right now logs written to Papertrail use the IP Address of the server its coming from instead of optionally leveraging use of the Hostname. I have added a boolean flag to the `NewPapertrailHook` on whether or not to write logs using the hostname or IP Address.

It is API breaking sadly, but could not think of a cleaner way of implementing it easily.

For those interested here are the changes I have implemented:

Pre:
```Oct 31    10:39:02     54.183.247.158    OurApp:     Configuration file loaded successfully.```

Post:
```Oct 31    11:00:04     ourserver-name    OurApp:     Configuration file loaded successfully.```