Tooltip position can be set on a per-step basis by setting an element's data-position to 'top', 'right', 'bottom', or 'left.

The "arrow" was refactored into its own element for cross-browser compatibility since :before can be problematic in <= IE8. Removed the timeout for moving the tooltip, as the delay was causing the tooltip not to size properly. Added _placeTooltip method that uses targetElement, tooltipLayer, and arrowLayer as parameters, then sets the appropriate CSS styles for the tooltipLayer.
Added read me instructions. Fixed default position.

Added instructions on how to use the 'data-position' attribute to the read me. Fixed the default position of the tooltip where it wasn't placing the tooltip at the bottom position unless specified as such; it now defaults to the bottom if no data-position is set. Ran the file through javascriptlint and fixed a couple small things.
Merge branch 'add_position_options' of https://github.com/casiotone/intro.js into casiotone-add_position_options
Fix some coding style problem, left and top position overlap with step number + rollback readme