Design refinements - Events listings

Some design refinements to events listings from Ben W:

- Add hover effect to event items, matches next-gen
- Increase font-weight for event-items and keep font-size consistent across breakpoints

**Hover before**
![hover-before mov](https://cloud.githubusercontent.com/assets/123386/5568710/159efac2-8f5a-11e4-8fb3-5e26f94fce0f.gif)

**Hover after**
![hover-after mov](https://cloud.githubusercontent.com/assets/123386/5568711/1aa9afee-8f5a-11e4-8736-60c5a69b5488.gif)

**Font-weight before**
![screen shot 2014-12-29 at 12 58 26](https://cloud.githubusercontent.com/assets/123386/5568741/7669b70c-8f5a-11e4-9449-326e271926c6.png)

**Font-weight after**
![screen shot 2014-12-29 at 12 49 45](https://cloud.githubusercontent.com/assets/123386/5568722/561969d4-8f5a-11e4-86de-4d7223a1b113.png)

![screen shot 2014-12-29 at 12 49 57](https://cloud.githubusercontent.com/assets/123386/5568724/5848033c-8f5a-11e4-949c-22a3e4b66be4.png)