Add request links functionality to the availability on the record view.

Closes #294 

There is a data-request-url attribute that is only populated if an item is requestable (meant to generate a request link from the live lookup).  If there is no `data-request-url` attribute then the item cannot be requested, otherwise it should get a request link if the item returns a due date.

#### Location request link
---
![location-request](https://cloud.githubusercontent.com/assets/96776/3365501/6f21600e-fb2f-11e3-89ce-00626ffe83f8.png)

#### Item request link
---
![item-level-request-links](https://cloud.githubusercontent.com/assets/96776/3365503/7946828a-fb2f-11e3-9b2b-7b4afab704c2.png)

#### Special SSRC request link
---
![ssrc-link](https://cloud.githubusercontent.com/assets/96776/3365505/83366404-fb2f-11e3-8d19-d78539612bf7.png)

Yeah, this was added at the last minute.  Let me try to explain my thinking and see if it makes sense to retain this API.

The thought here is there are two different levels of logic that can initiate a "location level request link".  It was only in `Holdings::Library` at first (as that's where the majority of these records exist) as a way to say ALL locations in this library should get location level request links (without having to configure it at the location level).

However; I noticed we have one edge case, which is the SSRC-DATA location.  This is a location w/i Green that also needs a link at the location level, however the logic only applies to a location w/i the library.  While this is the only example we have of this now, it also gives us the ability to extend this logic in the future if need be while retaining the same API in the UI (which is checking both the library and location to see if they are intended to get location level request links).