bigger install button hit target (bug 1055703)

Visual idea of what will now happen:
![](http://f.cl.ly/items/1p26202z1g0r140J3J3m/Image%202014-08-21%20at%202.00.28%20PM.png)

The actual way it looks:
![](http://f.cl.ly/items/0s1l000g1d0o2j0m1Q2b/Image%202014-08-21%20at%202.04.46%20PM.png)