chore: upgrade TS

package.json

@@ -41,7 +41,7 @@
     "rollup-plugin-terser": "^2.0.2",
     "rollup-plugin-typescript2": "^0.17.0",
     "ts-jest": "^23.10.0",
-    "typescript": "^3.0.3",
+    "typescript": "^3.1.3",
     "yorkie": "^2.0.0"
   }
 }