only apply introns-arrow left if the tooltip was not re-positioned

When the tooltip falls below the window, we reposition it to push up
into the existing viewport. This fix also adds in the proper arrow
styling so that it falls on the bottom of this tooltip and points to
the actual content.

Author: travispwingo

intro.js

@@ -473,8 +473,9 @@
           // Modify so that the bottom of the tooltip connects with the target
           arrowLayer.className = "introjs-arrow left-bottom";
           tooltipLayer.style.top = "-" + (tooltipHeight - targetOffset.height - 20) + "px"
+        } else {
+          arrowLayer.className = 'introjs-arrow left';
         }
-        arrowLayer.className = 'introjs-arrow left';
         break;
       case 'left':
         if (this._options.showStepNumbers == true) {