Label block

This replaces #362  and makes the text block a very simple label text block. 

It takes in a string, and a font size (in point values). 

It will:
* Rotate text with the sprite
* Move text to the end of the word
* Draws text at alphabetic baseline
* Always stamp LTR. There will need to be a bit of work done for RTL.

Example:
![screen shot 2014-06-29 at 10 22 34 am](https://cloud.githubusercontent.com/assets/1505907/3423921/a02170cc-ffb2-11e3-9d27-0bd111a033d5.png)

Ok, `stage.changed()` does work, and it _is_ necessary to still call it explicitly. If the call is left out, some text won't show until the specific area get damaged by doing something like dragging the sprite around.