Flow notification item new style

* Remove the snippet as requested

* Truncate topic title to 50 bytes

* Change the wording in notification message

Depends on:
https://gerrit.wikimedia.org/r/#/c/151792/
https://gerrit.wikimedia.org/r/#/c/151805/

Change-Id: Ic820319639dda869b7bb11809e75f6a2d023e16d
Merge "Flow notification item new style"