docs(readme): add testing requirements section

.gitignore

@@ -108,3 +108,6 @@ Gemfile.lock
 
 # copied `.md` files used for conversion to `.rst` using `m2r`
 docs/*.md
+
+# Vim
+*.sw?

docs/README.rst

@@ -62,6 +62,21 @@ Testing
 
 Linux testing is done with ``kitchen-salt``.
 
+Requirements
+^^^^^^^^^^^^
+
+* Ruby
+* Docker
+
+.. code-block:: bash
+
+   $ gem install bundler
+   $ bundle install
+   $ bundle exec kitchen test [platform]
+
+Where ``[platform]`` is the platform name defined in ``kitchen.yml``,
+e.g. ``debian-9-2019-2-py3``.
+
 ``kitchen converge``
 ^^^^^^^^^^^^^^^^^^^^