Fix Kuzzle version in Docker files (#94)

## What does this PR do ?
Fix Kuzzle version in Docker files (docker-compose & Dockerfiles) 

### How should this be manually tested?
Try to run the docker-compose.yml stack

### Other changes
Make the Readme looks great

Author: alexandrebouthinon

Dockerfile

@@ -1,4 +1,4 @@
-FROM kuzzleio/kuzzle
+FROM kuzzleio/kuzzle:1
 
 LABEL "io.kuzzle.vendor"="Kuzzle"
 

README.md

@@ -1,10 +1,32 @@
-[![Build Status](https://travis-ci.org/kuzzleio/kuzzle-plugin-cluster.svg?branch=master)](https://travis-ci.org/kuzzleio/kuzzle-plugin-cluster) [![codecov.io](http://codecov.io/github/kuzzleio/kuzzle-plugin-cluster/coverage.svg?branch=master)](http://codecov.io/github/kuzzleio/kuzzle-plugin-cluster?branch=master)
-
-# Cluster mode plugin
-
-This plugin adds a cluster mode to Kuzzle.
-
-## Kuzzle
+<p align="center">
+  <img src="https://user-images.githubusercontent.com/7868838/66303815-2617b000-e8fc-11e9-8c3f-613574be1746.png"/>
+</p>
+<p align="center">
+  <a href="https://david-dm.org/kuzzleio/kuzzle-plugin-cluster">
+    <img src="https://david-dm.org/kuzzleio/kuzzle-plugin-cluster.svg" />
+  </a>
+  <a href="https://travis-ci.com/kuzzleio/kuzzle-plugin-cluster">
+    <img alt="undefined" src="https://travis-ci.com/kuzzleio/kuzzle-plugin-cluster.svg?branch=master">
+  </a>
+  <a href="https://codecov.io/gh/kuzzleio/kuzzle-plugin-cluster">
+    <img src="https://codecov.io/gh/kuzzleio/kuzzle-plugin-cluster/branch/master/graph/badge.svg" />
+  </a>
+  <a href="https://github.com/kuzzleio/kuzzle-plugin-cluster/blob/master/LICENSE">
+    <img alt="undefined" src="https://img.shields.io/github/license/kuzzleio/kuzzle-plugin-cluster.svg?style=flat">
+  </a>
+</p>
+
+## About
+
+### Kuzzle Cluster Plugin
+
+This plugin adds a masterless cluster mode to Kuzzle.
+
+<p align="center">
+  :books: <b><a href="https://docs.kuzzle.io/core/1/guides/kuzzle-depth/scalability">Documentation</a></b>
+</p>
+
+### Kuzzle
 
 Kuzzle is a ready-to-use, **on-premises and scalable backend** that enables you to manage your persistent data and be notified in real-time on whatever happens to it. 
 It also provides you with a flexible and powerful user-management system.
@@ -15,15 +37,18 @@ It also provides you with a flexible and powerful user-management system.
 * :books: __[Documentation](https://docs.kuzzle.io)__
 * :email: __[Gitter](https://gitter.im/kuzzleio/kuzzle)__
 
-## Get trained by the creators of Kuzzle :zap:
+### Get trained by the creators of Kuzzle :zap:
 
 Train yourself and your teams to use Kuzzle to maximize its potential and accelerate the development of your projects.  
 Our teams will be able to meet your needs in terms of expertise and multi-technology support for IoT, mobile/web, backend/frontend, devops.  
 :point_right: [Get a quote](https://hubs.ly/H0jkfJ_0)
 
-## Compatibility
+### Compatibility matrice
 
-Kuzzle: >=1.8.0
+| Kuzzle Version | Plugin Version |
+| -------------- | -------------- |
+| 1.8.x          | 3.x.x          | 
+| 2.x.x          | 4.x.x          |
 
 ## Try it
 
@@ -33,7 +58,7 @@ To run a kuzzle stack, you can use the provided compose file:
 docker-compose up --scale kuzzle=3
 ```
 
-**NB: This compose stack is for tests and development only and should not be used as-is on production. ** 
+**NB: This compose stack is for tests and development only and should not be used as-is on production.** 
 
 ## Run a development stack
 
@@ -224,4 +249,3 @@ Here is a complete sample configuration using a 3 nodes redis cluster and a 2 el
 }
 
 ```
-

docker-compose.yml

@@ -1,3 +1,4 @@
+---
 version: "3"
 
 services:
@@ -11,10 +12,11 @@ services:
       - ./docker-compose/nginx/kuzzle.conf:/etc/nginx/conf.d/kuzzle.conf
 
   kuzzle:
-    image: kuzzleio/cluster
+    image: kuzzleio/kuzzle:1
     volumes:
-     - ./docker-compose/config/kuzzlerc.prod:/etc/kuzzlerc
+      - ./docker-compose/config/kuzzlerc.prod:/etc/kuzzlerc
     environment:
+      KUZZLE_PLUGINS: kuzzle-plugin-cluster
       NODE_ENV: ${NODE_ENV:-production}
       DEBUG: ${DEBUG:-none}
       DEBUG_COLORS: ${DEBUG_COLORS:-on}
@@ -28,4 +30,3 @@ services:
       nofile: 65536
     environment:
       cluster.name: kuzzle
-