Update guides regarding the extension changes

With rails/coffee-rails#61 (and #17241), the `.coffee` extension is
favoured over `.js.coffee`. Respectively, with rails/sass-rails#271
`.scss` and `.sass` are favoured over `.css.scss` and `.css.sass`.

Let's update the documentation to reflect that.

[ci skip]

guides/source/asset_pipeline.md

@@ -182,12 +182,12 @@ When you generate a scaffold or a controller, Rails also generates a JavaScript
 file (or CoffeeScript file if the `coffee-rails` gem is in the `Gemfile`) and a
 Cascading Style Sheet file (or SCSS file if `sass-rails` is in the `Gemfile`)
 for that controller. Additionally, when generating a scaffold, Rails generates
-the file scaffolds.css (or scaffolds.css.scss if `sass-rails` is in the
+the file scaffolds.css (or scaffolds.scss if `sass-rails` is in the
 `Gemfile`.)
 
 For example, if you generate a `ProjectsController`, Rails will also add a new
-file at `app/assets/javascripts/projects.js.coffee` and another at
-`app/assets/stylesheets/projects.css.scss`. By default these files will be ready
+file at `app/assets/javascripts/projects.coffee` and another at
+`app/assets/stylesheets/projects.scss`. By default these files will be ready
 to use by your application immediately using the `require_tree` directive. See
 [Manifest Files and Directives](#manifest-files-and-directives) for more details
 on require_tree.
@@ -424,7 +424,7 @@ $('#logo').attr({ src: "<%= asset_path('logo.png') %>" });
 This writes the path to the particular asset being referenced.
 
 Similarly, you can use the `asset_path` helper in CoffeeScript files with `erb`
-extension (e.g., `application.js.coffee.erb`):
+extension (e.g., `application.coffee.erb`):
 
 ```js
 $('#logo').attr src: "<%= asset_path('logo.png') %>"
@@ -525,8 +525,8 @@ The file extensions used on an asset determine what preprocessing is applied.
 When a controller or a scaffold is generated with the default Rails gemset, a
 CoffeeScript file and a SCSS file are generated in place of a regular JavaScript
 and CSS file. The example used before was a controller called "projects", which
-generated an `app/assets/javascripts/projects.js.coffee` and an
-`app/assets/stylesheets/projects.css.scss` file.
+generated an `app/assets/javascripts/projects.coffee` and an
+`app/assets/stylesheets/projects.scss` file.
 
 In development mode, or if the asset pipeline is disabled, when these files are
 requested they are processed by the processors provided by the `coffee-script`
@@ -538,13 +538,13 @@ web server.
 Additional layers of preprocessing can be requested by adding other extensions,
 where each extension is processed in a right-to-left manner. These should be
 used in the order the processing should be applied. For example, a stylesheet
-called `app/assets/stylesheets/projects.css.scss.erb` is first processed as ERB,
+called `app/assets/stylesheets/projects.scss.erb` is first processed as ERB,
 then SCSS, and finally served as CSS. The same applies to a JavaScript file -
-`app/assets/javascripts/projects.js.coffee.erb` is processed as ERB, then
+`app/assets/javascripts/projects.coffee.erb` is processed as ERB, then
 CoffeeScript, and served as JavaScript.
 
 Keep in mind the order of these preprocessors is important. For example, if
-you called your JavaScript file `app/assets/javascripts/projects.js.erb.coffee`
+you called your JavaScript file `app/assets/javascripts/projects.erb.coffee`
 then it would be processed with the CoffeeScript interpreter first, which
 wouldn't understand ERB and therefore you would run into problems.
 

guides/source/command_line.md

@@ -153,9 +153,9 @@ $ bin/rails generate controller Greetings hello
      create    app/helpers/greetings_helper.rb
      invoke  assets
      invoke    coffee
-     create      app/assets/javascripts/greetings.js.coffee
+     create      app/assets/javascripts/greetings.coffee
      invoke    scss
-     create      app/assets/stylesheets/greetings.css.scss
+     create      app/assets/stylesheets/greetings.scss
 ```
 
 What all did this generate? It made sure a bunch of directories were in our application, and created a controller file, a view file, a functional test file, a helper for the view, a JavaScript file and a stylesheet file.
@@ -241,11 +241,11 @@ $ bin/rails generate scaffold HighScore game:string score:integer
     create      app/views/high_scores/show.json.jbuilder
     invoke  assets
     invoke    coffee
-    create      app/assets/javascripts/high_scores.js.coffee
+    create      app/assets/javascripts/high_scores.coffee
     invoke    scss
-    create      app/assets/stylesheets/high_scores.css.scss
+    create      app/assets/stylesheets/high_scores.scss
     invoke  scss
-   identical    app/assets/stylesheets/scaffolds.css.scss
+   identical    app/assets/stylesheets/scaffolds.scss
 ```
 
 The generator checks that there exist the directories for models, controllers, helpers, layouts, functional and unit tests, stylesheets, creates the views, controller, model and database migration for HighScore (creating the `high_scores` table and fields), takes care of the route for the **resource**, and new tests for everything.

guides/source/generators.md

@@ -199,11 +199,11 @@ $ bin/rails generate scaffold User name:string
       create      app/views/users/show.json.jbuilder
       invoke  assets
       invoke    coffee
-      create      app/assets/javascripts/users.js.coffee
+      create      app/assets/javascripts/users.coffee
       invoke    scss
-      create      app/assets/stylesheets/users.css.scss
+      create      app/assets/stylesheets/users.scss
       invoke  scss
-      create    app/assets/stylesheets/scaffolds.css.scss
+      create    app/assets/stylesheets/scaffolds.scss
 ```
 
 Looking at this output, it's easy to understand how generators work in Rails 3.0 and above. The scaffold generator doesn't actually generate anything, it just invokes others to do the work. This allows us to add/replace/remove any of those invocations. For instance, the scaffold generator invokes the scaffold_controller generator, which invokes erb, test_unit and helper generators. Since each generator has a single responsibility, they are easy to reuse, avoiding code duplication.
@@ -409,7 +409,7 @@ $ bin/rails generate scaffold Comment body:text
       create      app/views/comments/show.json.jbuilder
       invoke  assets
       invoke    coffee
-      create      app/assets/javascripts/comments.js.coffee
+      create      app/assets/javascripts/comments.coffee
       invoke    scss
 ```