Add a little bit of documentation about the deployment feature

README.md

@@ -1,6 +1,47 @@
 # Gosen
 
 Gosen is a Ruby library for the [Grid'5000 RESTful API](https://api.grid5000.fr/).
+It relies on the [Restfully library](http://github.com/crohr/restfully) for interacting with the API.
+
+## Features
+
+Currently, it allows to submit deployments that retry automatically when too many nodes failed, similarly to [Katapult](http://www.loria.fr/~lnussbau/katapult.html).
+
+## Installation
+
+    $ gem install gosen
+
+## Usage
+
+The following example deploys the latest version of the Lenny-x64-big environment on the paramount-1 and paramount-2 nodes.
+If both nodes are not successfully deployed, Gosen retries again (in this case, at most 5 deployment are submitted).
+
+    #!/usr/bin/env ruby
+
+    require 'gosen'
+    require 'logger'
+    require 'restfully'
+
+    logger = Logger.new(STDOUT)
+
+    Restfully::Session.new(:configuration_file => '~/.grid5000') do |grid, session|
+      site = grid.sites[:rennes]
+      nodes = [ 'paramount-1.rennes.grid5000.fr', 'paramount-2.rennes.grid5000.fr' ]
+      deployment = Gosen::Deployment.new(site, 'lenny-x64-big', nodes,
+      {
+        :logger => logger,
+        :max_deploy_runs => 5,
+        :min_deployed_nodes => nodes.length,
+        :ssh_public_key => File.read(File.expand_path('~/.ssh/authorized_keys'))
+      })
+      deployment.join
+    end
+
+The logger allows to print information about the deployment, in a style similar to Katapult:
+
+    I, [2010-04-21T11:31:09.351803 #21673]  INFO -- : Kadeploy run 1 with 2 nodes (0 already deployed, need 2 more)
+    I, [2010-04-21T11:37:11.817323 #21673]  INFO -- : Nodes deployed: paramount-1.rennes.grid5000.fr paramount-2.rennes.grid5000.fr
+    I, [2010-04-21T11:37:11.817440 #21673]  INFO -- : Had to run 1 kadeploy runs, deployed 2 nodes
 
 ## Note on Patches/Pull Requests