Deprecate request.json property
Add test for deprecated flask.Request properties.
Merge pull request #1206 from methane/deprecate-request.json

Deprecate request.json property
Add changelog entry for #1206
Pass keyword args from `test_client` method to client class constructor
Add a little documentation regarding kwargs in the `app.test_client()` method
Add CHANGES entry and versionchanged entry to docstring
Merge branch 'test-client-kwargs'

Fix #992