Review branch

Created reviews mvc with one test, testing user creating review successfully.
Since this form is the same form as on the edit page, we can reduce duplication by extracting a partial.

To make a partial, you move the code for the form into a new file:

```html
<!-- app/views/reviews/_form.html.erb -->

<%= form_for [site, review] do |f| %>
  <% if @review.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@review.errors.count, "error") %> prohibited this article from being saved:</h2>
      <ul>
        <% @review.errors.full_messages.each do |msg| %>
          <li><%= msg %></li>
      </ul>
    </div>
  <% end %>

  <p>
    <%= f.label :rating %>
    <%= f.text_field :rating %>
  </p>

  <p>
    <%= f.label :description %>
    <%= f.text_area :body %>
  </p>

  <%= f.submit %>
<% end %>
```

Then you can reuse the form in both the edit and new templates:

```html
<!-- app/views/reviews/edit.html.erb %>

<h1>Edit Review </h1>

<%= render 'reviews/form', site: @site, review: @review %>
```

```html
<!-- app/views/reviews/new.html.erb %>

<h1>New Review </h1>

<%= render 'reviews/form', site: @site, review: @review %>
```

More about partials at
http://guides.rubyonrails.org/layouts_and_rendering.html#using-partials