fixing metadata tags to not be, um, empty

Author: vsoch

_includes/metadata.html

@@ -1,7 +1,7 @@
-<meta name="description" content="{% if page.summary %}{{ page.summary | strip_html | strip_newlines }}{% endif %}">
-<meta name="keywords" content="{{page.tags}}{% if page.tags %}, {% endif %} {{page.keywords}}">
+<meta name="description" content="{{ content | strip_html | strip_newlines }}">
+<meta name="keywords" content="{{ page.category }}">
 {% if page.title %}
-<meta name="name" content="{{ image.name }}">
+<meta name="name" content="{{ page.title }}">
 {% endif %}
 <meta name="thumbnail" content="http://singularity.lbl.gov/images/logo/logo.svg">
 {% if page.targz %}