Added support for common text decorations

This Pull Request adds support for common text decorations (like those found in css)
The pull defines 4 new style properties: 

- decoration:  `underline`, `overline`, `lineThrough`; you can specify more than a decoration in an array
- decorationStyle: `solid` (default), `dashed`, `dotted`, `double`, and `wavy`
- decorationColor: decoration(s) will be painted with this color 

You can also add a background to the text by specifying the `background` style property

this should close #10 and #69

![image](https://cloud.githubusercontent.com/assets/5453835/4180145/bfd88608-36e9-11e4-8510-edf2daf16fac.png)