Add memory increases report.

Summary:
This is based on the memory usage we're logging for 1% of instances.  It tries
to ignore memory which will be reclaimed after a few requests.
{F36660}

Test Plan:
Switched it to dump to a local file instead of emailing, ran the report
locally.

Reviewers: chris, csilvers

Reviewed By: csilvers

Subscribers: benkomalo, marcia, alan

Differential Revision: http://phabricator.khanacademy.org/D11481
Merge OOM emails into one.

Summary:
Now that we can put multiple tables in one email, we might as well use it!

Depends on D11481

Test Plan: Dumped to HTML and ran locally.

Reviewers: csilvers

Subscribers: marcia, chris, benkomalo, alan

Differential Revision: http://phabricator.khanacademy.org/D11524