no mutations

Author: Victor Saiz

src/components/themr.js

@@ -85,7 +85,7 @@ export default (componentName, localTheme, options = {}) => (ThemedComponent) =>
 function themeable(style = {}, theme) {
   if (!theme) return style
   return Object.keys(theme).reduce((result, key) => (
-    Object.assign(result, { [key]:
+    Object.assign({}, result, { [key]:
        style[key] && theme[key].indexOf(style[key]) === -1
        ? `${style[key]} ${theme[key]}`
        : theme[key] || style[key]