Fix issue with putSecond

1)
LruCache works incorrect. Methods like putSecond, putHour, putDay never works:
```scala
if (expireSec.toLong * 1000 < nowMs) None else Some(value)
```
```expireSec``` is just seconds without system time offset, for example:
putSecond("key", "value", 1) - expireSec == 1, 1000 always < System.currentTimeMillis(). 

I try to fix it in this pull request.

2) There are bug in docs:
http://ngocdaothanh.github.io/xitrum/guide/cache.html?highlight=cache#cache-object
```
Without an explicit TTL (time to live):

    put(key, value)

Without an explicit TTL: <<!!!! HERE (should be With an explicit TTL:)

    putSecond(key, value, seconds)
    putMinute(key, value, minutes)
    putHour(key, value, hours)
    putDay(key, value, days)
```

3) I add logback-test.xml but it does not works, no any logs are showing. I dont know why, it should works.