Display posts and users inline in insights notification email

Document Grunt handling email CSS inlining.
Hey, posts work pretty well. Also, I improved the fake post generator
for testing.
We now have users in emails, a fix for some posts in emails not
appearing, and the ability to generate many test users.
Fixed a handful of broken tests and wrote new ones for posts and users
in emails.
Throw an exception for unserialize() errors
Add test debugging helpers
- Add commented-out debugging info about what tests are running
- Comment out one-time and developer insight tests for faster runs
Stop testing on PHP 5.2

This is the beginning of our PHP 5.2 support deprecation.
See also #1830
https://github.com/ginatrapani/ThinkUp/issues/1830