Add category & mixture matches into search result view. Closes #3.

* Restore format to navigation links.
* Add style to fix position of 'search' text.
* Add class Searchable.
* Add implementation for searchable models.
* Change search queryset using search() method on manager.
* Add h1 header level to category name.
* Crop photos on carousel in home.
* Add category results to search view.
Add thumbnail presentation and modal for images. Closes #7

* Add holder.js library to create fake thumbnails.
* Change thumbnail format in mixture detail.
* Add modal for images.