[O] Fix TSLint: " should be '

src/components/navigation/navigation.ts

@@ -9,7 +9,7 @@ import Constants from '@/constants';
 })
 export default class Navigation extends Vue
 {
-    public activeIndex: string = "0";
+    public activeIndex: string = '0';
 
     @Prop() courses: any;
 

src/constants.ts

@@ -7,5 +7,5 @@ export default class Constants
      * Base url for api access
      * TODO: Use https for actual usage
      */
-    public static API_URL: string = "http://cn2.hydev.org:24021/api";
+    public static API_URL: string = 'http://cn2.hydev.org:24021/api';
 }