improve frontend aspects of install documentation

README.md

 
 You also need `redis-server` package if you want to send email in async mode.
 
+### Frontend dependencies ###
+
+[//]: # ( from https://nodejs.org/en/download/package-manager/#debian-and-ubuntu-based-linux-distributions)
+
+Install nodejs by typing:
+
+    curl -sL https://deb.nodesource.com/setup_7.x | sudo -E bash -
+    sudo apt-get install -y nodejs
+
+Check that this went well by getting npm version:
+
+    npm -v
+
+Then install frontend dependancies:
+
+    npm install
+
 ## Database ##
 
 If you want use PostgreSQL as database engine:
 * personalize home page (background image, title color...)
 * ...
 
+### frontend files compilation ###
+
+Considering your environment, run:
+
+    npm run gulp-dev
+
+or
+
+    npm run gulp-prod
+
 ### database schema ###
 
 The last step before to run the application is to initialize the database schema. This is done through the following command:

package.json

   "description": "",
   "main": "",
   "scripts": {
-    "test": "echo \"Error: no test specified\" && exit 1"
+    "test": "echo \"Error: no test specified\" && exit 1",
+    "gulp-dev": "gulp dev",
+    "gulp-prod": "gulp prod"
   },
   "repository": {
     "type": "git",