fix(theme): fix card and list colors for dark themes (#667)

Closes #350

src/components/card/card.scss

@@ -17,6 +17,7 @@ md-card {
   border-radius: $md-card-border-radius;
   font-family: $md-font-family;
   background: md-color($md-background, card);
+  color: md-color($md-foreground, base);
 }
 
 md-card:hover {

src/components/list/list.scss

@@ -42,6 +42,7 @@ based on whether the list is in dense mode.
     font-size: $font-size;
     height: $base-height;
     padding: 0 $md-list-side-padding;
+    color: md-color($md-foreground, base);
   }
 
   &.md-list-avatar .md-list-item {