little tweaks to like counts in topic list view

- like counts use number formatting (so 1100 is 1.1K like other counts)
- made 'likes' column wide enough to hold 3 digit and > 999 likes

revised earlier PR per comments - undid column swap and went back to center-alignment because it didn't look right with the column in this position...

![topic-likes](https://f.cloud.github.com/assets/2217652/756387/f9ec0148-e60a-11e2-83c4-8d0ca9220fc8.PNG)