chore(deps): update dependency typescript to v2.8.4

Author: renovate-bot

package.json

@@ -22,7 +22,7 @@
     "ts-jest": "21.2.4",
     "tslint": "5.8.0",
     "tslint-config-airbnb": "5.3.0",
-    "typescript": "2.8.1"
+    "typescript": "2.8.4"
   },
   "dependencies": {},
   "jest": {

yarn.lock

@@ -3127,9 +3127,9 @@ type-check@~0.3.2:
   dependencies:
     prelude-ls "~1.1.2"
 
-typescript@2.8.1:
-  version "2.8.1"
-  resolved "https://registry.yarnpkg.com/typescript/-/typescript-2.8.1.tgz#6160e4f8f195d5ba81d4876f9c0cc1fbc0820624"
+typescript@2.8.4:
+  version "2.8.4"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-2.8.4.tgz#0b1db68e6bdfb0b767fa2ab642136a35b059b199"
 
 uglify-js@^2.6:
   version "2.8.29"