Correct theme for Jekyll v3.1

> You are currently using the Jekyll Bootstrap framework
which has a known incompatibility with Jekyll v3.1. To fix this
incompatibility, change `page.theme.name` in `_includes/JB/setup`
to `layout.theme.name`. Your site may not build properly until this
change has been applied.

For more information, see http://jekyllrb.com/docs/upgrading/2-to-3/#layout-metadata.

Closes #8
Fixes #7
diff --git a/site/_includes/JB/setup b/site/_includes/JB/setup
index efcd84b..03d0966 100644
--- a/site/_includes/JB/setup
+++ b/site/_includes/JB/setup
@@ -16,7 +16,7 @@
     {% if site.JB.ASSET_PATH %}
       {% assign ASSET_PATH = site.JB.ASSET_PATH %}
     {% else %}
-      {% capture ASSET_PATH %}{{ BASE_PATH }}/assets/themes/{{ page.theme.name }}{% endcapture %}
+      {% capture ASSET_PATH %}{{ BASE_PATH }}/assets/themes/{{ layout.theme.name }}{% endcapture %}
     {% endif %}  
   {% endif %}
-{% endcapture %}{% assign jbcache = nil %}
\ No newline at end of file
+{% endcapture %}{% assign jbcache = nil %}