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 I really want is

* rename the block to 'print' 
* use 'px' instead of 'pt'
* get rid of the 'size' parameter and take the pen size attribute instead
* only actually render the text if the pen is "down", otherwise just move as in line 2785
* make sure not to draw  the default line in line 2785 if you're already printing text

What do you think?