RegexURLPattern and RegexURLResolver must be changed to URLPattern and URLResolver respectively

Not working for django=2.1.3 & djangorestframework==3.9.0

You need to change this:

- **URLPattern** and **URLResolver** on [line:3](https://github.com/manosim/django-rest-framework-docs/blob/94571d05617d24816ba8fdc5e836d17645a88319/rest_framework_docs/api_docs.py#L3), [line:26](https://github.com/manosim/django-rest-framework-docs/blob/94571d05617d24816ba8fdc5e836d17645a88319/rest_framework_docs/api_docs.py#L26), [line:29](https://github.com/manosim/django-rest-framework-docs/blob/94571d05617d24816ba8fdc5e836d17645a88319/rest_framework_docs/api_docs.py#L29) in api_docs.py file.
- **pattern.pattern.regex** on [line:27](https://github.com/manosim/django-rest-framework-docs/blob/94571d05617d24816ba8fdc5e836d17645a88319/rest_framework_docs/api_docs.py#L27) in api_docs.py file
- **pattern.pattern.regex.pattern** on [line:43](https://github.com/manosim/django-rest-framework-docs/blob/94571d05617d24816ba8fdc5e836d17645a88319/rest_framework_docs/api_docs.py#L43)
- **parent_pattern.pattern.regex.pattern** on [line:24](https://github.com/manosim/django-rest-framework-docs/blob/94571d05617d24816ba8fdc5e836d17645a88319/rest_framework_docs/api_endpoint.py#L24), [line:39](https://github.com/manosim/django-rest-framework-docs/blob/94571d05617d24816ba8fdc5e836d17645a88319/rest_framework_docs/api_endpoint.py#L39) and [line:40](https://github.com/manosim/django-rest-framework-docs/blob/94571d05617d24816ba8fdc5e836d17645a88319/rest_framework_docs/api_endpoint.py#L40) in api_endpoint.py file.

Ref: https://github.com/encode/django-rest-framework/pull/5500

Start by reading rest_framework_docs/api_docs.py at the referenced lines and rest_framework_docs/api_endpoint.py at lines 24, 39, and 40. Update the listed URL pattern and regex attribute references for Django 2.1.3, then verify that the documentation tooling works with django==2.1.3 and djangorestframework==3.9.0.

Written by the indexing model from the issue text.