Merge pull request #1708 from nilakshdas/1661-weeklybestsinsight-fix

Weekly Bests insight fix, closes #1661
Response time copy fix
Only bold key stats, not whole phrase
Favorited links insight copy tweak: brief is better, standardize on other posts with lists of items
[DB MIGRATION REQ'D] Delete old Weekly best insights for regeneration
Moved getSyntaticTimeDifference() to InsightTerms class
Merge pull request #1709 from AaronKalair/move-get-syntatic-time-difference

Moved getSyntacticTimeDifference() to InsightTerms class
Expand URLs plugin: Get the title and description of expanded links during crawl
Improve insight links template: show user avatar, link originating tweet
Add missing mock function
Added function to check conditions before generating insights