fix up memcached_status to work outside container

- use memcache module instead of telnet
- add version check
- return a list of predefined metrics
- add a api up/down boolean metric
```
root@infra2_memcached_container-afc67820:~# python kak 127.0.0.1; echo $?
Traceback (most recent call last):
  File "kak", line 57, in <module>
    main(args)
  File "kak", line 34, in main
    stats = item_stats(bind_ip, port)
  File "kak", line 23, in item_stats
    stats = mc.get_stats()[0][1]
IndexError: list index out of range
1
root@infra2_memcached_container-afc67820:~#
```

In my case memcached is bound to 192.168.18.60:11211 ... wondering if we should handle this specific case since I'm sure we'll run into it in production?