Update to use Streamhub SDK 2.6

- upgrade to be compatible with SDK 2.6 (include View module, use cajon)
- fix bug with setting bar width in HorizontalBarView (it's some side effect of view rendering in new SDK, my fix does "work" but you may want to review it because I don't know what's up)
- fix typo in MetricListView comparator calculation

This is in support of my other pull request for streamhub-hot-collections.  https://github.com/Livefyre/streamhub-hot-collections/pull/1