chore(package): update @angular/language-service to version 6.0.3

Closes #16

Author: greenkeeper[bot]

package.json

@@ -30,7 +30,7 @@
   "devDependencies": {
     "@angular/cli": "~1.7.1",
     "@angular/compiler-cli": "^5.2.0",
-    "@angular/language-service": "^5.2.0",
+    "@angular/language-service": "^6.0.3",
     "@types/jasmine": "~2.8.3",
     "@types/jasminewd2": "~2.0.2",
     "@types/node": "~9.4.6",