Added an option to have a responsive slider

If the slider width or height is set to 100% when you resize the window the slider tooltip doesn't change its position. With this modification you can set a 'data-slider-responsive' attribute that makes the tooltip moving properly on window resizing.
Update README.md
Added unit testing, examples and doc for responsive
Merge branch 'patch-1'

Conflicts:
	js/bootstrap-slider.js
Merge pull request #2 from zonia3000/master

Added unit testing, examples and doc for responsive