Linode DNS Authenticator (#5302)

* Added DNS based authenticator plugin for Linode

* Added linode plugin to docs

* Added Dockerfile

* Added .gitignore and readthedocs.org.requirements.txt

* Updated default_propagation_seconds

* Updated according to changes requested

* Bump version to 0.26.0

* Advertise our packages work on Python 3.7.

certbot-dns-linode/docs/index.rst

@@ -0,0 +1,28 @@
+.. certbot-dns-linode documentation master file, created by
+   sphinx-quickstart on Wed May 10 10:52:06 2017.
+   You can adapt this file completely to your liking, but it should at least
+   contain the root `toctree` directive.
+
+Welcome to certbot-dns-linode's documentation!
+====================================================
+
+.. toctree::
+   :maxdepth: 2
+   :caption: Contents:
+
+.. toctree::
+   :maxdepth: 1
+
+   api
+
+.. automodule:: certbot_dns_linode
+   :members:
+
+
+
+Indices and tables
+==================
+
+* :ref:`genindex`
+* :ref:`modindex`
+* :ref:`search`