chore(deps): update to kuromojin@2

Author: azu

package.json

@@ -46,8 +46,8 @@
     "prettier": "^1.10.2"
   },
   "dependencies": {
-    "kuromojin": "^1.4.0"
-},
+    "kuromojin": "^2.0.0"
+  },
   "prettier": {
     "singleQuote": false,
     "printWidth": 120,