100% test coverage

[LincolnPuzey]

there is only 1 uncovered line - either
a) remove it - breaking change.
b) add a test covering it.

[2019342a]

Is option a a breaking change? Looking at the line in question, it seems to have been introduced in #108 and by the discussion on the PR, it looks like it was a fix for Django less than 1.10.

Removing this

if field.get_attname() in instance.get_deferred_fields():
    continue

does not make the test fail (which I assume is what this test is trying to cover)