Here is a Github link to a lightweight and very easy to integrate library that enables you to play with borders as you want for any widget you want, simply based on a FrameLayout widget.
Here is a quick sample code for you to see how easy it is, but you will find more information on the link.
<com.khandelwal.library.view.BorderFrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
app:leftBorderColor="#00F0F0"
app:leftBorderWidth="10dp"
app:topBorderColor="#F0F000"
app:topBorderWidth="15dp"
app:rightBorderColor="#F000F0"
app:rightBorderWidth="20dp"
app:bottomBorderColor="#000000"
app:bottomBorderWidth="25dp" >
</com.khandelwal.library.view.BorderFrameLayout>
So, if you don't want borders on bottom, delete the two lines about bottom in this custom widget, and that's done.
And no, I'm neither the author of this library nor one of his friend ;-)