Add filmstrip to image collections

Closes #140 

* Added filmstrip viewer for digital image collections search records with `img_info` or `file_id` data
* Filmstrip jQuery plugin watches for `image-filmstrip` element and lazyloads images in a responsive filmstrip view

@jvine In addition to `prev` and `next`, added scrollbar to images' list for quick navigation (if there are 100+ items). Images are loaded one set at a time. 

PS: Please use the `SOLR_URL:.../solr/item-merge` test index to enable filmstrip view on Walters Manuscripts and other similar records

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![searchworks-issue140-1](https://cloud.githubusercontent.com/assets/302258/3132286/ae5f2fc4-e80d-11e3-9ec9-d73b47145c63.png)