Update documentation (#613)

Convert CONTRIBUTING from MD to rST
Fix rST syntax errors in README.rst
Remove deprecated Django version from README.rst
Add QA step for validating rST syntax

.travis.yml

@@ -5,6 +5,8 @@ python:
   - 3.7
   - 3.8
 env:
+  - TOXENV=qa
+
   - DJANGO=1.11 PACKAGE=pil
   - DJANGO=1.11 PACKAGE=imagemagick
   - DJANGO=1.11 PACKAGE=graphicsmagick

CONTRIBUTING.rst

@@ -0,0 +1,9 @@
+|Jazzband|
+
+This is a `Jazzband <https://jazzband.co/>`__ project. By contributing
+you agree to abide by the `Contributor Code of
+Conduct <https://jazzband.co/about/conduct>`__ and follow the
+`guidelines <https://jazzband.co/about/guidelines>`__.
+
+.. |Jazzband| image:: https://jazzband.co/static/img/jazzband.svg
+   :target: https://jazzband.co/

README.rst

@@ -5,7 +5,7 @@ Thumbnails for Django.
 Features at a glance
 ====================
 
-- Support for Django 1.11, 2.0, 2.1, 2.2 and 3.0 following the `Django supported versions policy`_
+- Support for Django 1.11, 2.2 and 3.0 following the `Django supported versions policy`_
 - Python 3 support
 - Storage support
 - Pluggable Engine support for `Pillow`_, `ImageMagick`_, `PIL`_, `Wand`_, `pgmagick`_, and `vipsthumbnail`_
@@ -73,7 +73,7 @@ Install in your project
 Then register 'sorl.thumbnail', in the 'INSTALLED_APPS' section of
 your project's settings. ::
 
-    INSTALLED_APPS = (
+    INSTALLED_APPS = [
         'django.contrib.auth',
         'django.contrib.admin',
         'django.contrib.sites',
@@ -83,7 +83,7 @@ your project's settings. ::
         'django.contrib.contenttypes',
 
         'sorl.thumbnail',
-    )
+    ]
 
 
 Templates Usage
@@ -131,7 +131,7 @@ You can use the 'get_thumbnail'::
 See more examples in the section `Low level API examples`_ in the Documentation
 
 Using in combination with other thumbnailers
--------------------------------------------
+--------------------------------------------
 
 Alternatively, you load the templatetags by {% load sorl_thumbnail %}
 instead of traditional {% load thumbnail %}. It's especially useful in
@@ -146,8 +146,8 @@ same name (``thumbnail``) for the templatetag module::
 Frequently asked questions
 ==========================
 
-Is so slow in Amazon S3 !
--------------------------
+Is so slow in Amazon S3!
+------------------------
 
 Possible related to the implementation of your Amazon S3 Backend, see the `issue #351`_
 due the storage backend reviews if there is an existing thumbnail when tries to

tox.ini

@@ -1,6 +1,6 @@
 [travis]
 python =
-  3.6: py36, flake8
+  3.6: py36
   3.7: py37
   3.8: py38
 
@@ -20,7 +20,7 @@ PACKAGE =
 [tox]
 skipsdist = True
 envlist =
-  flake8
+  qa
   py{36,37,38}-django{111,22,30}-{pil,imagemagick,graphicsmagick,redis,dynamodb,wand,pgmagick,dbm,vipsthumbnail}
 
 [testenv]
@@ -51,11 +51,13 @@ setenv =
 commands =
   py.test -rw --cov-config ../setup.cfg --cov sorl
 
-[testenv:flake8]
+[testenv:qa]
 changedir = {toxinidir}
 skip_install = True
 deps =
   flake8
   flake8-bugbear
+  rstvalidator
 commands =
   flake8 --show-source sorl/
+  python -m rstvalidator README.rst CHANGES.rst CONTRIBUTING.rst