Fix css layout

**Fix centering of years and months and homogenize the design of the widget between the views, including hours, minutes and seconds selectors.**

## Previews:

### Before (actual master) // After (suggested less compiled)
                        
![01-years](https://cloud.githubusercontent.com/assets/5930831/2681542/bb242fe8-c18e-11e3-8e0f-7ec79ead77be.png)
![02-months](https://cloud.githubusercontent.com/assets/5930831/2681551/c4eea436-c18e-11e3-9554-6e4c5aef072d.png)
![03-days](https://cloud.githubusercontent.com/assets/5930831/2681554/c7cba3de-c18e-11e3-897a-88fc083dbacb.png)
![04-time](https://cloud.githubusercontent.com/assets/5930831/2681611/455291dc-c18f-11e3-9690-85dea5dc929d.png)
![05-hours](https://cloud.githubusercontent.com/assets/5930831/2681559/cbf6f1de-c18e-11e3-9974-6a042c20d722.png)
![06-minutes](https://cloud.githubusercontent.com/assets/5930831/2681560/cf24988e-c18e-11e3-97d0-23ca35a0dc1a.png)
![07-seconds](https://cloud.githubusercontent.com/assets/5930831/2681564/d1b7dfb6-c18e-11e3-9673-596840cec387.png)

**Nota Bene:** I only commited the updated less file, I did not update the build (I have issues with my less compilator, seems different than yours).