Added demography pages for age, education, and gender

@rocha @lamagnifica @clintonb @shnayder @marcotuts 

* Demographics by age, education, and gender are added as as third nav
* Tooltips for charts and metrics are TBD (AN-3736)


Demographics by Age
![demographics-age](https://cloud.githubusercontent.com/assets/5265058/4653535/cca275aa-54ae-11e4-9b47-bd7fc90cdee3.png)


Demographics by Education
![demographics-edu](https://cloud.githubusercontent.com/assets/5265058/4653533/cc88c204-54ae-11e4-839a-2f61c31d6d9f.png)


Demographics by Gender
![demographics-gender](https://cloud.githubusercontent.com/assets/5265058/4653534/cc9811d2-54ae-11e4-9d31-11d36aa18825.png)
The current year is used by the calling method and others and thus passed in.  I don't see any harm in changing it (other than the very rare case that the year switches over and this method is being run), and your suggestion makes it more convenient too.