Various design improvements (#42)

There are a couple of minor improvements which customers solve at the moment with various hacks and should be part of the theme instead.

* Removed max-width from card excerpt

* Updated custom theme settings

- Added show/hide "Read more" section in posts
- Added drop-cap option for posts
- Added show/hide metadata for posts

* Added lock icon for members-only posts on list

* Updated excerpt logic to work with access levels

* Fixing missing id's for input fields

* Updated secondary color contrast

partials/components/cta.hbs

@@ -14,7 +14,7 @@
                             {{#if @custom.signup_subheading}}{{@custom.signup_subheading}}{{else}}{{@site.description}}{{/if}}
                         </p>
                     </div>
-                    {{> "email-subscription"}}
+                    {{> "email-subscription" email_field_id="cta-email"}}
                 </div>
             </section>
         {{/match}}