Update docs with templating changes

### Update dash/screen API docs
![screen shot 2014-04-30 at 2 42 06 pm](https://cloud.githubusercontent.com/assets/3514765/2845529/35f10090-d097-11e3-9c79-320442bace9c.png)


### Add "Guide to Templating" page
![screen shot 2014-05-02 at 2 59 22 pm](https://cloud.githubusercontent.com/assets/3514765/2866717/ed8c5430-d22b-11e3-9df0-d8d702419350.png)


![screen shot 2014-04-30 at 2 37 51 pm](https://cloud.githubusercontent.com/assets/3514765/2845482/9d0cfcc6-d096-11e3-8fbb-28ca72f2cce9.png)