Formly

* Add support for Django 3.1

**Backwards Incompatible Changes**
Drops support for Python 2.x and Django 1.x.

* Add the ability to remap `MULTIPLE_TEXT` answers
* Introduce `FORMLY_TEST_ARGS` pattern to run a restricted version of the test suite

**Backwards Incompatible Changes**
Previously, answers stored in `FieldResult.answer` for `Field`s with the `MULTIPLE_TEXT` field_type were getting serialized to JSON twice.

This release fixes this by:
- Removing extra serialization/de-serialization from the `compress` and `decompress` methods in the form field / widget
- Running a data migration that removes the double serialization for existing entries

* Add Django v1.11, 2.0 support
* Drop Django 1.8, 1.9, 1.10, and Python 3.3 support
* Add URL namespacing (i.e. urlname "formly_survey_results" is now "formly:survey_results") **Backwards Incompatible**
* Rename URL names, removing "dt_" and "rt_" prefixes **Backwards incompatible**
* Rename deletion view names, removing "View" suffix **Backwards incompatible**
* Move documentation into README and standardize layout
* Convert CI and coverage to CircleCi and CodeCov
* Add PyPi-compatible long description
* Add migration checking to test suite
* Fix several view errors