There are far too many variables and far too little work done here to keep waiting for
anything. There's one glaring TODO here, and that's filtering by tenant id. Other than
that, this is the simplest thing that could possibly work; no worker, no authentication,
no http pooling.

Comments welcome.
Use treq
Let klein deal with the changes it needs.
Use treq properly, assert all the things is test
Fix lint
Fix the tests
Sort out the query to hit the audit log with
Remove @fields
Fix lint
Merge from trunk
Fix the issues raised in review
Simplify elasticsearch query
Respond to review
Populate history fields based on availability
Remove the endpoint guard.
Ugh. Fix a c-n-p error
Just grab all possible fields from AUDIT_LOG_FIELDS
Copy over the message, if it exists (yay tests)
Get pagination working (that wasn't actually hard, if you'd read the stupid docs
Use the paginatable decorator