Improve alt text in Suggestoton curriculum

sites/en/intro-to-rails/CRUD_with_scaffolding.step

@@ -21,27 +21,27 @@ steps {
 
   step {
     message "Point your browser to [http://localhost:3000/topics](http://localhost:3000/topics)"
-    message "You should see a page listing topics that looks something like this:"
+    message "You should see the 'Listing Topics' page with headers for title and description, and a link to add a new topic:"
 
-    img src: "img/Seattle_topic_list_page.png", alt: "Topic List Page"
+    img src: "img/Seattle_topic_list_page.png", alt: "Screenshot of topic list page"
   }
 
   step {
     message <<-MARKDOWN
   * Click on "New Topic"
   * Fill in the form and click "Create Topic"
-  * You should see a confirmation page like this:
+  * You should see a page showing your new topic with a message that your topic was successfully created:
     MARKDOWN
 
-    img alt: "topic created", src: "img/Seattle_topic_created.png"
+    img alt: "Screenshot of topic detail page with confirmation message", src: "img/Seattle_topic_created.png"
   }
 
   step {
     message <<-MARKDOWN
       * Click on "back"
       * You should see the topic list again, this time with your new topic listed:
 
-      ![list with topic](img/Seattle_list_with_topic.png)
+      ![Screenshot of topic list with new topic](img/Seattle_list_with_topic.png)
 
       * Try the 'show', 'edit', and 'destroy' links to see what they do
       * You've created a basic database driven web site, congrats!

sites/en/intro-to-rails/deploying_to_heroku.step

@@ -101,7 +101,7 @@ explanation do
   MARKDOWN
 
   message "You should be able to deploy your application any time it's in a good, working state. Your typical workflow will look like:"
-  img src: "img/workflow.png", alt: "workflow", style: "border: none"
+  img src: "img/workflow.png", alt: "Diagram showing git workflow of making changes, committing them, and pushing to Heroku.", style: "border: none"
   ol do
     li { message "Add or change some code" }
     li { message "Commit your changes (`git commit`)" }

sites/en/intro-to-rails/getting_started.step

@@ -1,4 +1,4 @@
-img src: "img/Start_page.png", alt: "Start Page"
+img src: "img/Start_page.png", alt: "Screenshot of a Ruby on Rails default home page"
 
 goals do
   goal "Create Your New Application"
@@ -53,11 +53,11 @@ Open the suggestotron folder as a project in your text editor.
 
 In **Sublime Text 2**, you can use the `Project > Add Folder to Project...` menu option:
 
-<img src='img/sublime_add_folder_to_project.png' />
+![Sublime Text Project menu screenshot](img/sublime_add_folder_to_project.png)
 
-Select your `suggestotron` folder from the file picker that opens. If everything works out Sublime should look something like this:
+Select your `suggestotron` folder from the file picker that opens. If everything works out Sublime should show the directories of your app in a tree structure on the left:
 
-<img src='img/sublime_project_as_folder.png' />
+![Screenshot of Suggestotron project folder tree in Sublime Text](img/sublime_project_as_folder.png)
     MARKDOWN
   end
 

sites/en/intro-to-rails/intro-to-rails.step

@@ -12,7 +12,7 @@ allow users to:
 
 You've sketched up an initial screenshot of what you want it to look like:
 
-![screenshot](img/finished_app.png)
+![Browser window with topic titles that can be voted on, ordered by number of votes](img/finished_app.png)
 
 ### Meta-Goal
 

sites/en/intro-to-rails/setting_the_default_page.step

@@ -70,7 +70,7 @@ explanation {
 
   In Rails 4, you can also get this information on your site in development. Go to <a href="http://localhost:3000/rails/info">http://localhost:3000/rails/info</a> and you'll see something like this:
 
-  <img src='img/rails4_rails_info_routing.png'>
+  <img src='img/rails4_rails_info_routing.png' alt='Screenshot of browser-based Rails routing info page'>
 
   You'll also see that table in Rails 4 whenever you try to access an invalid route (try <a href="http://localhost:3000/sandwich">http://localhost:3000/sandwich</a>)