chore(package): update textlint-tester to version 2.1.0 (#56)

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -44,7 +44,7 @@
     "glob": "^7.0.0",
     "mocha": "^3.0.1",
     "textlint": "^7.1.0",
-    "textlint-tester": "^1.0.0"
+    "textlint-tester": "^2.1.0"
   },
   "dependencies": {
     "analyze-desumasu-dearu": "^2.1.2",