Added rounded and square image thumbnails

Added round and square corner image thumbnails. This should probably go through more testing. I tested it on a Samsung Galaxy S4. The default style is grey with the image dimensions inside. If an image is provided, it will fill the inside. NOTE: I added a new class called AutoResizeTextView, which is not my code. 
It is from http://stackoverflow.com/questions/5033012/auto-scale-textview-text-to-fit-within-bounds/17782522#17782522. I made a comment in the code to source where it is from. It resizes the dimensions text(200x150) to fit the size of the thumbnail. The smaller the thumbnail, the smaller the font gets.

Rounded
![thumbnails_rounded](https://f.cloud.github.com/assets/684942/1661225/c83cb5fa-5bd7-11e3-9145-b4cc49f8c87f.png)

Square
![thumbnails_square](https://f.cloud.github.com/assets/684942/1661226/d1116f2c-5bd7-11e3-9447-3143c912e3b0.png)

Here is how to create a default thumbnail and a thumbnail with a provided image

           <com.beardedhen.androidbootstrap.BootstrapThumbnail
                android:id="@+id/thumbnailTwo"
                android:layout_width="wrap_content"
        	    android:layout_height="wrap_content"
                bootstrapthumbnail:bt_width="150dp"
                bootstrapthumbnail:bt_height="110dp"
                android:layout_margin="10dp"/>
            
            <com.beardedhen.androidbootstrap.BootstrapThumbnail
                android:id="@+id/thumbnailTwo"
                android:layout_width="wrap_content"
        	    android:layout_height="wrap_content"
                bootstrapthumbnail:bt_width="150dp"
                bootstrapthumbnail:bt_height="110dp"
                android:layout_margin="10dp"
                bootstrapthumbnail:bt_image="@drawable/bbuton_danger"/>

You can set the image programmatically as well by calling setImage().
Let me know if there are any features I should add.