Update __init__.py in base

Author: Anders Fredrik Kiær

dash_core_components_base/__init__.py

@@ -135,5 +135,13 @@
     },
 ])
 
+_css_dist = [
+    {
+        'relative_package_path': '{}.css'.format(__name__),
+        'namespace': 'dash_core_components',
+    }
+]
+
 for _component in __all__:
-    setattr(locals()[_component], '_js_dist', _js_dist)
+    setattr(locals()[_component], '_js_dist', _js_dist)
+    setattr(locals()[_component], '_css_dist', _css_dist)