Merge branch 'develop' of github.com:mermaid-js/mermaid into develop

src/diagrams/flowchart/styles.js

@@ -62,6 +62,14 @@ const getStyles = options =>
     stroke-width: 1px;
   }
 
+  .cluster text {
+    fill: ${options.titleColor};
+  }
+
+  .cluster span {
+    color: ${options.titleColor};
+  }
+
   div.mermaidTooltip {
     position: absolute;
     text-align: center;