React.renderComponent --> React.render

Also fixed a spelling mistake.

docs/02.2-jsx-spread.md

@@ -6,7 +6,7 @@ prev: jsx-in-depth.html
 next: jsx-gotchas.html
 ---
 
-If you know all the properties that you want to place on a component a head of time, it is easy to use JSX:
+If you know all the properties that you want to place on a component ahead of time, it is easy to use JSX:
 
 ```javascript
   var component = <Component foo={x} bar={y} />;

docs/06-transferring-props.md

@@ -37,7 +37,7 @@ var FancyCheckbox = React.createClass({
     );
   }
 });
-React.renderComponent(
+React.render(
   <FancyCheckbox checked={true} onClick={console.log}>
     Hello world!
   </FancyCheckbox>,
@@ -70,7 +70,7 @@ var FancyCheckbox = React.createClass({
     );
   }
 });
-React.renderComponent(
+React.render(
   <FancyCheckbox checked={true} onClick={console.log}>
     Hello world!
   </FancyCheckbox>,