fix colorpicker in panel. Fixes #396

Summary: Overflow on panels was clipped. Setting overflow visible to make it visible.

Reviewed By: passy

Differential Revision: D14519402

fbshipit-source-id: 264f99e3ac20986365c8f69564c4633818dd4a94

src/ui/components/Panel.js

@@ -112,6 +112,7 @@ export default class Panel extends React.Component<
     borderTop: 'none',
     flexGrow: 1,
     padding: props.padded ? 10 : 0,
+    overflow: 'visible',
   }));
   state = {
     collapsed: this.props.collapsed == null ? false : this.props.collapsed,