Supports transparent image.

The engine assumed the source image must be opaque,
so it redraws the background instead of clearing the canvas,
this doesn't work for image with transparent parts.
Merge pull request #39 from b123400/transparent-image

Supports transparent image.
-Use options object
-Need only Image element ID
Style changes
-Removed redundant code
-Update help file text
-Resize canvas when element resizes
-Hide canvas when mouse over element to make it useable
-All options passed as object
Update Readme file
Add option to auto hide rain effect on mouse hover,
this allows interaction to used image.
-Update  readme file
#43 adjustments
Update README.md.

Specify the language used for the demo.
Fix a few JSHint warnings.
Update demo.html.

* specify a doctype
* specify lang
* specify meta charset
* remove type for css and js files
* add alt tag for img
Merge pull request #48 from XhmikosR/master

various
type fix
#5 simplify drop rendering
Update README.md.
Fix JSHint error.
Merge pull request #51 from XhmikosR/master

various-3