Remove shadow under ActionBar

It's only happened for 4.4.2 and above. Both Yote Shin and Kabyar has this :stuck_out_tongue_winking_eye: . But I guess we should get rid of the shadow in BUM. 

#### Before
![screenshot_2014-10-01-14-01-33 2 - - - - - - - -](https://cloud.githubusercontent.com/assets/275120/4471772/9a3a3ab0-493e-11e4-8038-61d8e52e1f3f.png)

#### After
![screenshot_2014-10-01-14-10-07 2 - - - - - - - -](https://cloud.githubusercontent.com/assets/275120/4471778/a697dbc8-493e-11e4-8878-175937cc2e39.png)