Merge pull request #196 from nschulzke/nschulzke-overview-scene-md

Fix a few code snippets in the guides

Thank you Nathan!

Author: boydm

guides/overview_graph.md

@@ -11,7 +11,7 @@ one thing. When multiple primitives are put together, almost any standard UI can
 For example, the graph below shows the words "Hello World" around them.
 
     @graph Graph.build(font: :roboto, font_size: 24)
-      |> text("Hello World", text_align: center, translate: {300, 300})
+      |> text("Hello World", text_align: :center, translate: {300, 300})
       |> circle(100, stroke: {2, :green}, translate: {300, 300})
 
 In the example above, the first line creates a new graph and assigns two font styles to its root. The next two lines form a pipeline that adds primitives to the root

guides/overview_scene.md

@@ -52,7 +52,7 @@ whose helper function is imported from the `Scenic.Components` module.
 
         @graph Graph.build()
           |> text("Hello World", font_size: 22, translate: {20, 80})
-          |> button({"Do Something", :btn_something}, translate: {20, 180})
+          |> button("Do Something", translate: {20, 180})
 
         def init( _scene_args, _options ) do
           {:ok, @graph, push: @graph}