Bump gitbook version

gaearon · gaearon · commit cbaeb99038ca · 2015-09-03T16:42:32.000+03:00
diff --git a/book.json b/book.json
@@ -1,5 +1,5 @@
 {
-  "gitbook": "2.2.0",
+  "gitbook": "2.3.0",
   "structure": {
     "summary": "docs/README.md"
   },
