Update topNavigation.php

This small changes will look the navigation beautiful on mobile device with addition of small icon. I also rename the id="search-menu" with id="top-dropdown-menu" since "search-menu" is already used for search section.
Update _layout.php

add class login-screen to make login box not too down from the top
Update theme.css

add class login-screen to make login box not too down
Update profileHeader.php

Changes to make mobile view much better :)
Merge pull request #302 from sonyarianto/master

Update topNavigation.php