Expose base object in entity wrapper classes

This allows easier debugging.

Also remove an outdated comment in the SDK source.
When formatting relative dates, use "0s"

Instead of empty string, display "0s" (or "Posted 0s ago")
when time past is smaller than 0.5s or lies in the future.
Merge pull request #24 from Livefyre/rc2

When formatting relative dates, use "0s"