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.

Author: Ben M

README.md

@@ -8,10 +8,10 @@ Intro.js can be added to your site in three simple steps:
 
 **1)** Include `intro.js` and `introjs.css` (or the minified version for production) in your page.
 
-**2)** Add `data-intro` and `data-step` to your HTML elements.  
+**2)** Add `data-intro` and `data-step` to your HTML elements. You can optionally set the tooltip's position by adding `data-position`. The default position is 'bottom'.
 For example: 
 ```html
-<a href='http://google.com/' data-intro='Hello step one!' data-step='1'></a>
+<a href='http://google.com/' data-intro='Hello step one!' data-step='1' data-position='right'></a>
 ````
 
 **3)** Call this JavaScript function:

intro.js

@@ -77,8 +77,8 @@
             //right arrow
             _nextStep.call(self);
           }
-        };
-      }
+        }
+      };
     }
     return false;
   }
@@ -111,8 +111,9 @@
    * @method _nextStep
    */
   function _previousStep() {
-    if(this._currentStep == 0)
+    if(this._currentStep == 0){
       return;
+    }
 
     _showElement.call(this, this._introItems[--this._currentStep].element);
   }
@@ -158,14 +159,15 @@
         tooltipLayer.style.right = "-" + (tooltipLayerPosition.width + 10) + "px";
         arrowLayer.className = 'introjs-arrow left';
         break;
-      case 'bottom':
-        tooltipLayer.style.bottom = "-" + (tooltipLayerPosition.height + 10) + "px";
-        arrowLayer.className = 'introjs-arrow top';
-        break;
       case 'left':
         tooltipLayer.style.left = "-" + (tooltipLayerPosition.width + 10) + "px";
         arrowLayer.className = 'introjs-arrow right';
         break;
+      case 'bottom':
+      default:
+        tooltipLayer.style.bottom = "-" + (tooltipLayerPosition.height + 10) + "px";
+        arrowLayer.className = 'introjs-arrow top';
+        break;
     }
   }