Remove tabIndex (schrodinger#347)

* Remove tabIndex
* Set tab index if keyboardPageEnabled or keyboardScrollEnabled is true

Author: ifabbe

src/FixedDataTable.js

@@ -798,15 +798,18 @@ var FixedDataTable = createReactClass({
           style={{top: footOffsetTop}}
         />;
     }
-
+    var tabIndex = null
+    if (this.props.keyboardPageEnabled || this.props.keyboardScrollEnabled) {
+      tabIndex = 0
+    }
     return (
       <div
         className={joinClasses(
           this.state.className,
           cx('fixedDataTableLayout/main'),
           cx('public/fixedDataTable/main'),
         )}
-        tabIndex={0}
+        tabIndex={tabIndex}
         onKeyDown={this._onKeyDown}
         onWheel={this._wheelHandler.onWheel}
         onTouchStart={this._touchHandler.onTouchStart}

src/Scrollbar.js

@@ -186,8 +186,7 @@ var Scrollbar = createReactClass({
         onWheel={this._wheelHandler.onWheel}
         className={mainClassName}
         ref={this.rootRef}
-        style={mainStyle}
-        tabIndex={0}>
+        style={mainStyle}>
         <div
           ref={this.faceRef}
           className={faceClassName}