Bundled varnish support

This pull request add's bundled varnish support to poky. When the work is 
complete, the user will be able to launch poky with varnish situated in front
to handle caching.

```
      |
     \|/
-------------
|  varnish  |
-------------
      |
     \|/
-------------
|   poky    |
-------------
      |
     \|/
-------------
| postgres  |
-------------
```

To do:
- [x] add something to probe in poky (/status)
- [x] add probes in varnish for backend (poky) health
- [x] offset the key-value api with /kv/:bucket/:key. this will enable /status support
- [x] add wrapper script for launching both varnish and poky
- [x] capistrano deploy
- [x] add fall through route for anything other than /kv or /status
- [ ] update modified_at on set*
- [x] add modified_at to the HTTP header for GET



Integration testing to do:
- [x] test POST, PUT, & DELETE purge the URL
- [x] test proper hit
- [x] test proper miss

These last there were done interactively.