New 'title' classes (replaces existing heading styles); Updated demo to reflect changes

New heading/title styles(#274):
![image](https://cloud.githubusercontent.com/assets/706039/3475704/fddd9b2a-02f3-11e4-8910-8f7388323dd3.png)

While I was at it, I added 'tabs' styles as a new component (#8) and converted demo pages to use tabsets (#383):
![image](https://cloud.githubusercontent.com/assets/706039/3503176/79eddff0-062c-11e4-921c-37c3d9ebd805.png)