Check for links from 2 days ago midnight untl an hour ago in LinkPrompt insight.

strtotime('midnight today') was generating a time at 00:00:00 on the
current day which would exclude many recent tweets and cause a confusing
insight to be generated.
Merge pull request #1759 from cdmoyer/1620-Link-Prompt-generating-nudge-for-real-recent-posts

Check for links from 2 days ago midnight untl an hour ago in LinkPrompt Insight closes #1620