Added option to change duration of animation.

Animation duration has been set as a property to the widget.
The default value is still 400, but now it can be changed with setDuration(value)
Added line to show how to change animation duration

Added line to show how to change duration of animaion
Added duration variable to animation options

On my previous commit I forgot to add the duration variable to the animation options.
Merge pull request #4 from HarkDev/master

Added Duration Option instead of static duration.
updated readme and bumped version
added simple example with dynamic menu
 change to readme