Update typescript to 2.6.2

Author: wmonk

packages/react-scripts/package.json

@@ -38,15 +38,15 @@
     "promise": "8.0.1",
     "raf": "3.4.0",
     "react-dev-utils": "4.2.1",
+    "source-map-loader": "^0.2.1",
     "style-loader": "0.19.0",
+    "sw-precache-webpack-plugin": "0.11.4",
     "ts-jest": "^20.0.7",
     "ts-loader": "^2.3.7",
     "tslint": "^5.7.0",
     "tslint-loader": "^3.5.3",
     "tslint-react": "^3.2.0",
-    "typescript": "~2.5.3",
-    "source-map-loader": "^0.2.1",
-    "sw-precache-webpack-plugin": "0.11.4",
+    "typescript": "^2.6.2",
     "url-loader": "0.6.2",
     "webpack": "3.8.1",
     "webpack-dev-server": "2.9.4",