fix(date-fns): fix duplicate module declaration typescript errors

Author: Matt Lewis

package.json

@@ -123,9 +123,8 @@
   },
   "dependencies": {
     "@ng-bootstrap/ng-bootstrap": "^1.0.0-alpha.0",
-    "@types/date-fns": "0.0.2",
     "angular-resizable-element": "~0.5.0",
     "calendar-utils": "0.0.36",
-    "date-fns": "^1.3.0"
+    "date-fns": "^1.11.1"
   }
 }

test/entry.ts

@@ -2,6 +2,7 @@
 /// <reference types="chai" />
 /// <reference types="sinon" />
 /// <reference types="sinon-chai" />
+/// <reference path="../node_modules/date-fns/typings.d.ts" />
 
 import 'core-js';
 import 'zone.js/dist/zone';