docs(readme): update README, add badges

docs/README.rst

-=====
-nginx
-=====
+.. _readme:
 
-Install nginx either by source or by package.
+nginx-formula
+=============
 
-.. note::
+|img_travis| |img_sr|
 
+.. |img_travis| image:: https://travis-ci.com/saltstack-formulas/nginx-formula.svg?branch=master
+   :alt: Travis CI Build Status
+   :scale: 100%
+   :target: https://travis-ci.com/saltstack-formulas/nginx-formula
+.. |img_sr| image:: https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg
+   :alt: Semantic Release
+   :scale: 100%
+   :target: https://github.com/semantic-release/semantic-release
 
-    See the full `Salt Formulas installation and usage instructions
-    <http://docs.saltstack.com/en/latest/topics/development/conventions/formulas.html>`_.
+Formula to set up and configure nginx
+
+.. contents:: **Table of Contents**
+
+General notes
+-------------
+
+See the full `SaltStack Formulas installation and usage instructions
+<https://docs.saltstack.com/en/latest/topics/development/conventions/formulas.html>`_.
+
+If you are interested in writing or contributing to formulas, please pay attention to the `Writing Formula Section
+<https://docs.saltstack.com/en/latest/topics/development/conventions/formulas.html#writing-formulas>`_.
+
+If you want to use this formula, please pay attention to the ``FORMULA`` file and/or ``git tag``,
+which contains the currently released version. This formula is versioned according to `Semantic Versioning <http://semver.org/>`_.
+
+See `Formula Versioning Section <https://docs.saltstack.com/en/latest/topics/development/conventions/formulas.html#versioning>`_ for more details.
+
+Contributing to this repo
+-------------------------
+
+**Commit message formatting is significant!!**
+
+Please see :ref:`How to contribute <CONTRIBUTING>` for more details.
 
 Available states
 ================
     :local:
 
 ``nginx``
-------------
+---------
 
 Meta-state for inclusion of all states.
 
 first available in the Helium release.
 
 ``nginx.pkg``
---------------------
+-------------
 
 Installs nginx from package, from the distribution repositories, the official nginx repo or the ppa from Launchpad.
 
 ``nginx.src``
---------------------
+-------------
 
 Builds and installs nginx from source.
 
 ``nginx.certificates``
--------------------
+----------------------
 
 Manages the deployment of nginx certificates.
 
 ``nginx.config``
--------------------
+----------------
 
 Manages the nginx main server configuration file.
 
 ``nginx.service``
---------------------
+-----------------
 
 Manages the startup and running state of the nginx service.
 
 ``nginx.servers_config``
---------------------------
+------------------------
 
 Manages virtual host files. This state only manages the content of the files
 and does not bind them to service calls.
 
 ``nginx.servers``
--------------------
+-----------------
 
 Manages nginx virtual hosts files and binds them to service calls.
 
 ``nginx.passenger``
-----------------------
+-------------------
 
 Installs and configures Phusion Passenger module for nginx. You need to enable
 the upstream phusion passenger repository with `install_from_phusionpassenger: true`.
 Nginx will also be installed from that repository, as it needs to be modified to
 allow the passenger module to work.
-