fixed range calculation for lazyLoad

center mode requires different range calculation as slidesToShow/2
slides are displayed before and after the current slide.
Updated Readme to reflect correct callback parameters
checking for perspective property for better css3 detection
fixing ms prefix checking
Merge pull request #461 from colbyfayock/old_opera

Add perspective feature detection for prefixes
Merge pull request #456 from ricardojr/master

Updated Readme to reflect correct callback parameters
Merge pull request #453 from acritox/fix_lazyload_range

fixed range calculation for lazyLoad
Added support for variable-width carousel slides (with demo)