Implement view helper

Implements the `contentful` view helper object. Still needs tests though. @jenius, if we could pair for a sec on how to test something like this, I'm not too sure where to start.

You only need to set the `id` property on content types to get data. If the `name` option is not given for a content type, I fetch the content types name, underscore it, pluralize it, and attach it to the contentful object using that name (e.g. content type with name 'Blog Post' => `contentful.blog_posts`).

Also, I left a Contentful token in the repo because it made it easy to test my work. I'll reset the token before we make this public.

cc / @kylemac @jenius