Change series_title precedence

Close #95

templates/_includes/_defaults.html

@@ -54,13 +54,6 @@
 {% set COMMENTS_INTRO = COMMENTS_INTRO %}
 {% endif %}
 
-{# Label to show with multi-part plugin widget #}
-{% if not SERIES_TITLE %}
-{% set SERIES_TITLE = 'Series' %}
-{% else %}
-{% set SERIES_TITLE = SERIES_TITLE %}
-{% endif %}
-
 {# Author's twitter handle. Used in Twitter card meta data #}
 {% if not TWITTER_USERNAME %}
 {% set TWITTER_USERNAME = '' %}

templates/_includes/multi_parts.html

@@ -1,11 +1,10 @@
 {% if article.metadata.parts_articles %}
-    {% if article.series_title %}
+    {%if SERIES_TITLE %}
+        <h4>{{ SERIES_TITLE }}</h4>
+    {% elif article.series_title %}
         <h4>{{ article.series_title }}</h4>
     {% else %}
-        {% from '_includes/_defaults.html' import SERIES_TITLE with context %}
-        {%if SERIES_TITLE %}
-            <h4>{{ SERIES_TITLE }}</h4>
-        {% endif %}
+        <h4>{{ article.parts }}</h4>
     {% endif %}
     <ul class="multi-parts-list">
         {% for part_article in article.metadata.parts_articles %}