add example user compser.json

bibtexbrowser-documentation.wiki

@@ -517,7 +517,21 @@ php bibtexbrowser-cli.php mybib.bib --id classical --set-title \"a new title\" -
 ====How to use with composer?====
 Bibtexbrowser can now be downloaded with composer, though not yet with packagist.
 
+In your project's `composer.json`, you must add this repo to the `repositories` section. As well, you must specify version `dev-master`, for now:
+````JSON
+{
+    "repositories": [
+	{
+	    "type": "vcs",
+	    "url": "https://github.com/monperrus/bibtexbrowser.git"
+	}
+    ],
+    "require": {
+        "monperrus/bibtexbrowser": "dev-master"
+    }
+}
 
+````
 
 =====Related tools=====