Add markdown support

Markdown support added for episode synopsis and review body.  Test added for episode synopsis markdown support.  Review body markdown support test dependent on review test suite.
There are plenty of other reasons why the page would not have that content.

Once you move the markdown rendering to a helper (as described above) you can more easily test this behavior with a unit test.

```ruby
# app/spec/helpers/application_helper_spec.rb

describe ApplicationHelper do
  describe "#render_markdown" do
    it "converts markdown to html" do
      html = helper.render_markdown("**bold** *italics*)
      expect(html).to eq "<b>bold</b> <i>italics</i>"
    end
  end
end
```

Thats just sudo code so im not sure if it works but something like that should work.