Match icon colors of speech bubbles from the mocks.

Closes https://github.com/steffanc/Tahoe/issues/69.
 
Shrink 9 PNG's so they can be expanded.   9.png files can not be shrunk so we must start with a smaller size.

![image](https://f.cloud.github.com/assets/326857/1507655/817e3ba6-499a-11e3-95f2-9d2e0b7d3fe4.png)

 
Create a SpeechBubbleIconGenerator to match colors of the speech bubbles.