Factor out image components

Author: danvk

tests/runner.html

@@ -33,6 +33,7 @@
   <script src="../webdiff/static/js/file_diff.js"></script>
 
   <script type="text/jsx;harmony=true" src="../webdiff/static/js/util.js"></script>
+  <script type="text/jsx;harmony=true" src="../webdiff/static/js/image.jsx"></script>
   <script type="text/jsx;harmony=true" src="../webdiff/static/js/components.jsx"></script>
 
   <script src="util_test.js"></script>