Lightbox galleries

This is the first implementation of lightbox galleries. Trails that link to galleries will instead load the content in a lightbox.

Fire away!

![lg-1](https://f.cloud.github.com/assets/518943/762027/6768ace0-e7e0-11e2-90dd-fa4baf09eeec.png)
![overlay-loading](https://f.cloud.github.com/assets/518943/762039/bdd01cee-e7e0-11e2-9359-5a08228c70a4.png)
![lg-2](https://f.cloud.github.com/assets/518943/762028/6b1aa366-e7e0-11e2-8901-71656efe8280.png)
![lg-3](https://f.cloud.github.com/assets/518943/762031/6da9ef6a-e7e0-11e2-896d-2240b4014d7f.png)