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)

What's going to be the most common usecase you can think of? Clearly @brianharvey was imagining "labelling" graphs. Most commonly what people are going to want to do is to *center* the label both vertically and horizontally. For this, an alphabetic baseline sucks, because it's nearly impossible to determine how to move the sprite vertically in order to achieve just that.