Fixed code block wrapping on export

Now wraps instead of running off the page.

Fixed #676

resources/assets/sass/export-styles.scss

@@ -13,4 +13,15 @@
 table {
   border-spacing: 0;
   border-collapse: collapse;
+}
+
+// Prevent code block overflow on export
+pre {
+  padding-left: 12px;
+}
+pre:after {
+  display: none;
+}
+pre code {
+  white-space: pre-wrap;
 }