Pagination support

This adds support for badgekit-api's pagination introduced in https://github.com/mozilla/badgekit-api/pull/113.  Pagination is accomplished via an optional "options" argument to functions that return arrays of objects (getBadges, getSystems, etc).

For example:

```
getBadges(context, { pagination: { page: 1, count: 10 }}, callback);
``` 

The callback also now receives an additional argument `pageData` in the event that pagination is requested.  This object looks like:

```
{ page: 1, count: 10, total: 104 }
```