Adding UI Bootstrap Slider component

- bower updated to include dependencies and also state overrides to pull in only necessary files
- index.html updated to import dependencies
- app.js updated to add the dependency to the app
- controllers.js updated to define the title and template HTML for the component demo and also set `sliderValue` on the `$scope`
- add both the `angular-bootstrap-slider` directive and `bootstrap-slider.min.js` to `/libs`
- adding demo file `ui-bootstrap-slider.html` to showcase the slider