Add option to hide underline + couple minor tweaks

This pull request adds the ability to hide the underline in the main edittext view, while automatically adjusting the positioning of the views drawn below (it will move them up to fill the now-empty space and look natural). I tested this pretty thoroughly (see "complex" example screenshot), but you should test this out thoroughly as well since spacing can be finicky.

This addresses #26 and possibly #27 (CC @egor-n)

I've attached a couple of screenshots at the bottom, but didn't update the README in this request so you can style it they way you like :)

Couple other tweaks in 7458e49 and e9e3038 dealing with the sample activity UI

Simple example:
![screenshot 2014-11-29 04 41 54](https://cloud.githubusercontent.com/assets/1361086/5234467/1fabfd20-7782-11e4-8bd7-46365e78e906.png)

Complex example (code not changed in this pull request):
![screenshot 2014-11-29 04 42 22](https://cloud.githubusercontent.com/assets/1361086/5234468/1faea746-7782-11e4-96a1-f2865f92a957.png)

Sample activity layout tweak with spacing at top and bottom of header:
![2014-11-29 12 33 26](https://cloud.githubusercontent.com/assets/1361086/5234464/ef1fd21c-7781-11e4-9159-1e7b03f249d7.png)