Added option (enabled by default) to allow initiate dragging by pressing anywhere similar to the framework implementation.
Also added some tweaks to avoid initiating a drag when touching outside the thumb if the component is inside a scrolling container.
NOTE: the way to know if it's a scrolling container used is API>=14, I'm not sure if anything can be done for ower API levels.
This commit closes #1, but it doesn't provide animated seeking as Samsung's implementation seems to do. Code contributions are welcome :)