Fixed misspellings. (reactjs#176)

lessons/03-navigating-with-link/README.md

@@ -4,7 +4,7 @@ Perhaps the most used component in your app is `Link`. Its almost
 identical to the `<a/>` tag you're used to except that its aware of
 the `Router` it was rendered in.
 
-Lets create some navigation in our `App` component.
+Let's create some navigation in our `App` component.
 
 ```js
 // modules/App.js

lessons/05-active-links/README.md

@@ -25,8 +25,8 @@ You can also use an active class name instead of inline-styles.
 <li><Link to="/repos" activeClassName="active">Repos</Link></li>
 ```
 
-We don't have a stylesheet on the page yet though. Lets add one--extra
-points if you can add a `link` tag from memory.
+We don't have a stylesheet on the page yet though. Lets add one-extra
+point if you can add a `link` tag from memory.
 
 ```html
 <link rel="stylesheet" href="index.css" />

lessons/11-productionish-server/README.md

@@ -88,7 +88,7 @@ app.get('*', function (req, res) {
 })
 ```
 
-We also need to tell wepback to build to this new directory:
+We also need to tell webpack to build to this new directory:
 
 ```js
 // webpack.config.js

lessons/12-navigating/README.md

@@ -1,10 +1,10 @@
 # Navigating Programatically
 
-While most navigation happens with `Link`, you can programatically
+While most navigation happens with `Link`, you can programmatically
 navigate around an application in response to form submissions, button
 clicks, etc.
 
-Let's make a little form in `Repos` that programatically navigates.
+Let's make a little form in `Repos` that programmatically navigates.
 
 ```js
 // modules/Repos.js