Add title to document (#743)

* Add title to API document

* Add title to Style Guide document

Author: munierujp

src/v2/api/index.md

@@ -1,4 +1,5 @@
 ---
+title: API
 type: api
 updated: 2018-02-10
 ---

src/v2/style-guide/index.md

@@ -1,4 +1,5 @@
 ---
+title: スタイルガイド
 type: style-guide
 updated: 2017-12-20
 ---
@@ -1727,8 +1728,8 @@ computed: {
 >
   Error: {{ error }}
 </div>
-<div 
-  v-else 
+<div
+  v-else
   key="search-results"
 >
   {{ results }}