Migrate to Typescript 1.5.3

Fixes #627

Tools/Gulp/package.json

@@ -7,7 +7,7 @@
     "gulp": "^3.8.11",
     "gulp-uglify": "~1.2.0",
     "gulp-sourcemaps": "~1.5.2",
-    "typescript": "~1.4.0",
+    "typescript": "~1.5.3",
     "gulp-typescript": "~2.6.0",
     "through2": "~0.6.5",
     "gulp-util": "~3.0.4",