changed gutter and weekend background fill opacity

Sara and i made the two week design cleaner. (ignore half filled circles)

Before:
![screen shot 2014-06-03 at 14 00 25](https://cloud.githubusercontent.com/assets/25203/3159813/b83c8166-eb16-11e3-8e34-7b6f0ff2c560.png)

After:
![screen shot 2014-06-03 at 13 59 18](https://cloud.githubusercontent.com/assets/25203/3159806/9f50f47a-eb16-11e3-8078-83c669454829.png)