Fixed a typo in index.html

Author: ekse

index.html

@@ -44,7 +44,7 @@ <h3><i class="fa fa-magic"></i> Straightforward</h3>
 
     <div class="col-md-4">
       <h3><i class="fa fa-file-text"></i> Header Only</h3>
-      There are no external tools requied, no preprocessor, no libraries, just your C++11 compliant compiler.
+      There are no external tools required, no preprocessor, no libraries, just your C++11 compliant compiler.
     </div>
 
     <div class="col-md-4">