feat(back-to-top): Add new back-to-top React component to docs

Signed-off-by: Geoff Pleiss <gpleiss@pivotal.io>

package.json

@@ -46,7 +46,6 @@
     "gulp-zip": "^2.0.2",
     "jshint-stylish": "^1.0.0",
     "npm": "^2.7.5",
-    "pui-react-back-to-top": "0.0.2",
     "q": "^1.0.1",
     "react-fa": "^3.0.0",
     "require-dir": "^0.1.0",
@@ -72,6 +71,7 @@
     "mkdirp": "^0.5.0",
     "node-sass": "^2.1.1",
     "pui-react-alerts": "^0",
+    "pui-react-back-to-top": "0.0.5",
     "pui-react-buttons": "^0",
     "pui-react-collapse": "^0",
     "pui-react-dividers": "^0",
@@ -85,10 +85,10 @@
     "pui-react-lists": "^0",
     "pui-react-media": "^0",
     "pui-react-modals": "^0",
-    "pui-react-overlay-trigger": "^0",
     "pui-react-notifications": "^0",
-    "pui-react-panes": "^0",
+    "pui-react-overlay-trigger": "^0",
     "pui-react-panels": "^0",
+    "pui-react-panes": "^0",
     "pui-react-radio": "^0",
     "pui-react-radio-group": "^0",
     "pui-react-ribbons": "^0",

src/pivotal-ui/components/back-to-top/back-to-top.scss

@@ -20,6 +20,22 @@ You can place the link anywhere in your markup, but best practices are either to
 ```
 */
 
+/*doc
+---
+title: Back to Top
+name: back_to_top_react
+categories:
+  - React Beta
+---
+
+You can use this component to scroll to the top of a page.
+
+The button will be fixed to the bottom right hand corner of the page.
+
+You can place the link anywhere in your markup, but best practices are either towards the top or bottom of your markup.
+
+```react_wrapped_example
+<UI.BackToTop/>
 ```
 */
 

src/pivotal-ui/javascripts/components.js

@@ -115,5 +115,7 @@ module.exports = {
   ErrorAlert: require('pui-react-alerts').ErrorAlert,
 
   OverlayTrigger: require('pui-react-overlay-trigger').OverlayTrigger,
-  Tooltip: require('pui-react-tooltip').Tooltip
+  Tooltip: require('pui-react-tooltip').Tooltip,
+
+  BackToTop: require('pui-react-back-to-top').BackToTop
 };