Move Wagtail FilePreviews from Misc to Media

Following discussion in #41.

README.md

@@ -113,6 +113,7 @@ Awesome Wagtail [![Awesome](https://cdn.rawgit.com/sindresorhus/awesome/d7305f38
 - [wagtailmedia](https://github.com/torchbox/wagtailmedia) - A Wagtail module for managing video and audio files within the admin.
 - [wagtail-embedvideos](https://github.com/infoportugal/wagtail-embedvideos) - Simple app that works similar to wagtailimages, but for embedding YouTube and Vimeo videos and music from SoundCloud. It's an integration of [django-embed-video](https://github.com/yetty/django-embed-video).
 - [Wagtail Alt Generator](https://github.com/marteinn/wagtail-alt-generator) - A module for generating image description and tags based on computer vision.
+- [Wagtail FilePreviews](https://github.com/filepreviews/wagtail-filepreviews) - Extend Wagtail's Documents with image previews and metadata from FilePreviews.io.
 
 ### Translations
 
@@ -140,7 +141,6 @@ Awesome Wagtail [![Awesome](https://cdn.rawgit.com/sindresorhus/awesome/d7305f38
 - [Wagtail Sharing](https://github.com/cfpb/wagtail-sharing) – Easier sharing of Wagtail drafts.
 - [Wagtail Postgres Search Backend](https://github.com/leukeleu/wagtail-pg-search-backend) - PostgreSQL full text search backend for Wagtail CMS.
 - [Wagtail Gridder](https://github.com/wharton/wagtailgridder) - Grid card layout similar to Google image search results, with an expanded area for card details.
-- [Wagtail FilePreviews](https://github.com/filepreviews/wagtail-filepreviews) - Extend Wagtail's Documents with image previews and metadata from FilePreviews.io
 
 ## Tools