[#518] Adds date-time tooltip to the activity time
[#518] formatter now give x months ago etc
[#518] Refactor render_datetime
[#518] Add time_ago_from_datestamp() helper
[#518] Deprecate time_ago_in_words_from_str() helper
[#518] Fixes for activity stream item template
Merge branch '518-date-time-within-activity-streams'