Task popup

Since @ZayneS will provide a detailed design, I don't tweak the UI too much.

![screen shot 2014-09-23 at 10 13 52 pm](https://cloud.githubusercontent.com/assets/1242553/4383709/99f1d918-43a9-11e4-839d-302af454a6b3.png)

If you remove this line, `monthly view` will turn out to be unusable. Why you remove this controller? This task directive is used in multiple views. You should simply add these functions to TaskController.