chore(package): update @angular/language-service to version 5.1.0

Closes #19

Author: greenkeeper[bot]

package.json

@@ -37,7 +37,7 @@
   "devDependencies": {
     "@angular/cli": "1.2.4",
     "@angular/compiler-cli": "^4.0.0",
-    "@angular/language-service": "^4.0.0",
+    "@angular/language-service": "^5.1.0",
     "@types/jasmine": "2.5.53",
     "@types/node": "~8.0.13",
     "angular-cli-ghpages": "^0.5.1",