add "publish up" and "publish down" dates on widgets

this is a full implementation of the feature request #127
![screen shot 2014-08-15 at 4 38 14 pm](https://cloud.githubusercontent.com/assets/2604749/3931429/fd686f78-2457-11e4-9644-9bcb1b73f608.png)
![screen shot 2014-08-15 at 4 38 21 pm](https://cloud.githubusercontent.com/assets/2604749/3931428/fd611778-2457-11e4-8cae-1a9d3ba088fa.png)
![screen shot 2014-08-15 at 4 42 04 pm](https://cloud.githubusercontent.com/assets/2604749/3931433/0f74a2cc-2458-11e4-9d4b-a9e954a1cd15.png)