fix(docs): Capitalize "URL".

Author: brettcannon

docs/content/tutorial/step_10.ngdoc

@@ -40,7 +40,7 @@ function PhoneDetailCtrl($scope, $routeParams, $http) {
 </pre>
 
 In the `PhoneDetailCtrl` controller, we created the `mainImageUrl` model property and set its
-default value to the first phone image url.
+default value to the first phone image URL.
 
 We also created a `setImage` event handler function that will change the value of `mainImageUrl`.
 
@@ -66,7 +66,7 @@ We bound the `ngSrc` directive of the large image to the `mainImageUrl` property
 We also registered an {@link api/ng.directive:ngClick `ngClick`}
 handler with thumbnail images. When a user clicks on one of the thumbnail images, the handler will
 use the `setImage` event handler function to change the value of the `mainImageUrl` property to the
-url of the thumbnail image.
+URL of the thumbnail image.
 
 <div style="display: none">
 TODO!