improvments: removed use of images, added color and size properties

0.3 Improvments:
 - The plugin no longer uses images for sparks (should load faster and gives the freedom to change the color without modifying the image)
 - properties minPixel and maxPixel used to specify the min and max size of the fireflies
 - color property used to specify the color of the fireflies
 
 Example:
 
 $.firefly({
 	color: '#fff',
 	minPixel: 1,
 	maxPixel: 3,
 	total : 65,
 	on: 'header'
 });