Force gitbook to use version 2.5.x

SamyPesse · SamyPesse · commit b5a8caebbc3a · 2015-11-05T11:14:26.000+01:00
diff --git a/book.json b/book.json
@@ -21,5 +21,5 @@
         }
     },
 
-    "gitbook": "2.1.0"
+    "gitbook": ">=2.5.2"
 }
