update Bootstrap URLs and branding

See http://getbootstrap.com/about/#brand
and twbs/bootstrap#9899
Removed defunct Download link
Added link to the new-ish official Bootstrap Expo.

Author: cvrebert

README.md

@@ -203,10 +203,10 @@
         + [Underscore.js](http://underscorejs.org/)
     + CSS
         + [A collection of best frameworks](http://usablica.github.io/front-end-frameworks/compare.html?v=2.0)
-        + Twitter Bootstrap
-            + [Home Page](http://twitter.github.com/bootstrap/)
-            + [Github](https://github.com/twitter/bootstrap/)
-            + [Download](http://twitter.github.com/bootstrap/assets/bootstrap.zip)
+        + Bootstrap
+            + [Home Page](http://getbootstrap.com/)
+            + [GitHub](https://github.com/twbs/bootstrap/)
+            + [Bootstrap Expo](http://expo.getbootstrap.com/)
             + [Bootstrap Hero List](http://www.bootstraphero.com/the-big-badass-list-of-twitter-bootstrap-resources): The big badass list of bootstrap resources
             + Widgets
                 + [Color and Date Picker](http://www.eyecon.ro/colorpicker-and-datepicker-for-twitter-bootstrap.htm)