include base .CodeMirror themed settings via `&`

css/helios.less

@@ -19,13 +19,13 @@ html[xmlns] .clearfix {
 	height: 1%;
 }
 
-.cm-s-helios.CodeMirror {
-	font-family: Menlo, Monaco, Consolas, Inconsolata, "Lucida Console", Courier, monospace;
-	line-height: 16px;
-	font-size: 13px;
-}
-
 .cm-s-helios {
+	&.CodeMirror {
+		font-family: Menlo, Monaco, Consolas, Inconsolata, "Lucida Console", Courier, monospace;
+		line-height: 16px;
+		font-size: 13px;
+	}
+
 	.CodeMirror-gutter.stops {
 		width: 20px;
 	}