Update section heading captions

Author: jordanmccullough

index.html

@@ -33,7 +33,7 @@ <h1>Open source materials</h1>
 <section class="screen-shot">
   <div class="container center">
     <a name="slides"></a>
-    <h2>Slides, no software necessary</h2>
+    <h2>Slide decks right in your browser</h2>
     <p>
       We've created a slide deck for each class we offer.<br>
       Just launch any class and present from the web browser.
@@ -66,7 +66,7 @@ <h3>Advanced</h3>
 <section class="grey workbook">
   <div class="container center">
     <a name="workbook"></a>
-      <h2>Workbook</h2>
+      <h2>Workbook for teaching narratives</h2>
       <p>
         Teach or learn from GitHub's very own class curriclum narrative.<br>
         From outline to full workflow, learn everything Git and GitHub.
@@ -83,7 +83,7 @@ <h2>Workbook</h2>
 <section class="downloads">
   <div class="container center">
     <a name="downloads"></a>
-    <h2>Downloads</h2>
+    <h2>Downloads to reference anytime</h2>
     <p>
       Looking for a quick reference sheet of Git commands?<br>
       These are the resources for you.