Handle new post pagination in Facebook graph API.

Updated testdata with new comments and page feeds from live graph explorer.
Update tests with new expected values.
Update crawler to look for pagination->next property rather than comments->count

Closes #1757, closes #1668
Docs: Clarify PHP code style guide
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.