fix video formatting

_includes/video.html

@@ -1,4 +1,4 @@
-<video height="240" controls>
+<video controls>
     <source src="{{ include.src }}" type="video/{{ include.type }}">
 
     Your browser does not support the HTML video tag. 

css/style.scss

@@ -222,6 +222,8 @@ small {
     margin-bottom: 20px;
 
     video {
+        max-width: 100%;
+        max-height: 240px;
         display: block;
         margin-left: auto;
         margin-right: auto;