chore(package): update @angular/forms to version 5.2.1

Closes #15

Author: greenkeeper[bot]

package.json

@@ -64,7 +64,7 @@
     "@angular/compiler": "^4.0.0",
     "@angular/compiler-cli": "^4.0.0",
     "@angular/core": "^4.0.0",
-    "@angular/forms": "^4.0.0",
+    "@angular/forms": "^5.2.1",
     "@angular/platform-browser": "^4.0.0",
     "@angular/platform-browser-dynamic": "^4.0.0",
     "@compodoc/compodoc": "^1.0.0-beta.9",