Additional feature

[mubashirqasim]

Hi Sandro,

Excellent work in making this library. I have a couple of questions if they are possible to address in the new features:

1. Is it possible to make a theme with alternating row colors (like provided in googleVis charts)
   

2. Is it possible to use different fill patterns based on a variable? Something like the following:
   

The patternplot package works with ggplot to achieve this. However, this capability is not available in any other timeline visualization library.

Many thanks,

Mubashir