Add blog post create template

Usually a `create` action would redirect to another route instead of rendering a template directly. But for the sake of keeping this tutorial simple, we'll just go ahead and render it--so we add a `create` template file. We leave it empty since that's all we need to do to get past the current error.

Outer red: expected to find text "Hello, World!" in ""

The next error is that, after submitting the blog post, the acceptance test expects to see the title of the post somewhere on the page, but it doesn't see it--because we haven't actually rendered any content at all.

app/views/blog_posts/create.html.erb

@@ -0,0 +1 @@
+<%# empty view %>