Saved search email improvements [MJ-895, MJ-896]

- Add activation link to saved searches of inactive users
- Send saved searches to inactive users
- Add activation window countdown

I changed the counter when there is less than one day remaining from "In X days, your activation window will expire" to "Your activation window will expire today". I thought that might be more pleasing than the alternative.

I think we could draw more attention to these. Maybe have the counter in red or something.

All tests pass.

![2014-06-25-090035_674x542_scrot](https://cloud.githubusercontent.com/assets/3379265/3385315/dfc6436c-fc68-11e3-80c5-0bdd6ac13b60.png)