Drop-In Directory Links

Refs #1 

## Implementation

To embed the directory links with a given selection on the page, simply include the script where the content should be injected.

```html
<script type="text/javascript"
  src="/widgets/links?subject=5&category=3"></script>
```

## Advanced Usage of Built-In Template
```html
<script type="text/javascript"
  src="/widgets/links?subject=5&category=3"
  class="[this class will be injected onto the container]"
  class-item="[this class will be injected onto each link]"
  action-text="[this text will precede each final form link in the directory link]"
></script>
```

## Custom Templates
```html
<script type="text/html" id="mywidget">
    <p ng-repeat="school in schools | orderBy:'name' | limitTo:5">
      <a ng-href="https://schools.collegedegrees.com/forms/{{ school.slug }}">
      <img ng-src="https://schools.collegedegrees.com/images/logos/{{ school.slug}}.250x70.png" /></a>
    </p>
</script>

<script type="text/javascript"
  src="/widgets/links?subject=5&category=3"
  template="mywidget"
></script>
```

## Target Injection
```html
<div id="mytarget"></div>

<script type="text/javascript"
  src="/widgets/links?subject=5&category=3"
  target="mytarget"
></script>
```

## Notes
- The same widget **`src="/widgets/links?subject=5&category=3"`** url can be used multiple times on a page with the same or different templates.  This script will only be requested from the server once but still implemented appropriately in each unique location.
- The server should (and does in this demo) send back proper expiry headers to prevent reloading of same widget urls across multiple pages within the site
- The server should (but does not yet) cache both the feed requests and responses
- The widget template should be included in a non-angular section of the page.  Otherwise angular will try to parse the content before the directive can see and interpret it.

## Preview
[http://localhost:3000/widgets/links/test](http://localhost:3000/widgets/links/test)