Load post-vote page scrolled down so social links are visible.

# Changes
 - Adds an anchor so we can link to the flash message and page will load scrolled down.
 - Redirects to flash message anchor after voting, so that user doesn't have to scroll to see share links.

/cc @angaither 

![barry-firstapp](https://cloud.githubusercontent.com/assets/583202/5187212/8bf60eda-7499-11e4-8767-cf4330139b2a.jpg)