adding docs

docs/using-scenario.md

@@ -1 +1,27 @@
-TODO
+Scenario is based on a json explaining how the backup will work.
+It contains 2 bases :
+  - backup (what you're going to backup)
+  - transport (how and where you're going to backup)
+
+# backup
+  - must begin with an uppercase
+  - a PHP class with the same name must exists in the Backup folder
+
+# transport
+  - must begin with an uppercase
+  - a PHP class with the same name must exists in the Transport folder
+
+# configuration of backup and transport
+  - all protected variable of the aimed class can be used as a configuration
+  
+# tips 
+## JSON
+The JSON must be compatible with the [PHP `json_decode`](http://php.net/manual/en/function.json-encode.php) implementation which correspond to [this one](http://www.faqs.org/rfcs/rfc4627.html)
+
+Basically :
+  - everything surrounded by " and no '
+  - no comments
+  - escape escape escape
+  
+
+