Make footer more visible

Before

![no
border](http://cl.ly/image/3I2r1S1B1F27/Screen%20Shot%202014-04-27%20at%
2012.05.12.png)

After

![with
border](http://cl.ly/image/1b3U0R312e0i/Screen%20Shot%202014-04-27%20at%
2012.05.27.png)
Replace MAIN_COLOR by (old) new CSS var spec
Merge pull request #151 from putaindecode/footer-big-border

Make footer more visible