Merge pull request #995 from ellisonbg/design30

Fixing markdown cell margin

src/notebook/cells/index.css

@@ -50,6 +50,8 @@
 
 .jp-MarkdownOutput-content {
   flex: 1 1 auto;
+  margin-top: 0.5em;
+  margin-bottom: 0.5em;
 }