#37 Missing setter for fillGradient

[fsanjurjo]

There\'s a property on simile\'s Plotinfo object, fillGradient, that has not counterpart on timeplotz\'s Plotinfo class so it\'s impossible to create charts with solid colours as by default Simile Plotinfo object is created with fillGradient set to true.

It would be great if you added a setter for this property to Plotinfo implementation.