have specific styles @import the base styles

this clarifies the value of what was formerly "style.css" a bit, and
also opens the door for potential styles that don't inherit the base
styling at all

incorporealcms/static/css/dark.css

@@ -1,3 +1,5 @@
+@import '/static/css/base.css';
+
 html {
     color: #CCC;
 }

incorporealcms/static/css/light.css

@@ -1,3 +1,5 @@
+@import '/static/css/base.css';
+
 html {
     color: #222;
 }

incorporealcms/templates/base.html

@@ -7,7 +7,6 @@
 <meta property="og:url" content="{{ base_url }}">
 <meta name="twitter:card" content="summary_large_image">
 <meta name="viewport" content="width=device-width, initial-scale=1">
-<link rel="stylesheet" href="{{ url_for('static', filename='css/style.css') }}">
 <link rel="stylesheet" href="{{ url_for('static', filename=user_style) }}">
 <link rel="icon" href="{% if config.FAVICON %}{{ config.FAVICON }}{% else %}{{ url_for('static', filename='img/favicon.png') }}{% endif %}">