Use hyphen instead of en dash (#907)

Author: stevenjoezhang

layout/index.swig

@@ -2,7 +2,7 @@
 {% import '_macro/post.swig' as post_template %}
 {% import '_macro/sidebar.swig' as sidebar_template %}
 
-{% block title %}{{ title }}{% if theme.index_with_subtitle and subtitle %} – {{ subtitle }}{% endif %}{% endblock %}
+{% block title %}{{ title }}{% if theme.index_with_subtitle and subtitle %} - {{ subtitle }}{% endif %}{% endblock %}
 
 {% block page_class %}
   {% if is_home() %}page-home{% endif -%}