docs(tutorial/2 - Angular Templates): Update docs for running the unit test

Update docs for running the unit test using karma. Explain some extra configuration to make if user only has one browser either Chrome of Firefox.

Author: risan

docs/content/tutorial/step_02.ngdoc

@@ -195,13 +195,28 @@ to ensure that Karma and its necessary plugins are installed. You can do this by
 
 To run the tests, and then watch the files for changes: `npm test`.
 
-* Karma will start new instances of Chrome and Firefox browser automatically. Just ignore them and let them run in
+* Karma will start new instances of Chrome and Firefox browsers automatically. Just ignore them and let them run in
    the background. Karma will use these browsers for test execution.
-* If you only have Chrome browser installed on your machine, make sure to update the karma configuration file before 
-   running the test. Update `unit/test/karma.conf.js` file to only include Chrome browser:
-   
+* If you only have one browser installed on your machine (either Chrome or Firefox browser), make sure to update the 
+   karma configuration file before running the test. Locate the configuration file in `test/karma.conf.js`, then
+   update the property of `browsers` to suit with the one you have in your machine.
+  
+  If you only have Chrome browser installed: 
+  <pre>
+    ...
+    frameworks: ['jasmine'],
+    
+    browsers: ['Chrome'],
+    ...
+  </pre>
+  
+  Or if you only have Firefox browser installed:
   <pre>
-    browsers: ['Chrome']
+    ...
+    frameworks: ['jasmine'],
+    
+    browsers: ['Firefox'],
+    ...
   </pre>
 
 * You should see the following or similar output in the terminal: