Out-of-the-box Oj uses :object mode, this shifts us to use :compat mode
by default which is safer.
It means any de-serialization going forward will default to this mode.
If we wish to serialize or deserialize arbitrary objects going forward with
no json interfaces we will have to opt in.
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
