Sort by vote(!)

# What Changed
* When you click on Votes column header, the titles table sorts. It sorts by descending by default.
* Sort by ascending or descending.
* Added an arrow next to the votes column, to indicate whether it is ascending or descending.
* When a title is added or a vote is made, sorting updates.

# Potential Issues
* I don't have the entire showbot stack running locally, but I *think* it'll work just fine.
* I wasn't sure if this should go in `showbot.js`, so I put it in its own file (`client.js`). Please change this however you see fit.