build: limit typescript version to patches

Author: clydin

package.json

@@ -91,7 +91,7 @@
     "stylus": "^0.54.5",
     "stylus-loader": "^3.0.1",
     "tree-kill": "^1.0.0",
-    "typescript": "^2.6.2",
+    "typescript": "~2.6.2",
     "uglifyjs-webpack-plugin": "^1.1.5",
     "url-loader": "^0.6.2",
     "webpack": "~3.10.0",