fix(package): update material-ui to version 0.19.0

Author: greenkeeper[bot]

package.json

@@ -98,7 +98,7 @@
   "dependencies": {
     "@travi/travi.org-theme": "0.2.0",
     "bootstrap-sass": "3.3.7",
-    "material-ui": "0.18.7",
+    "material-ui": "0.19.0",
     "microformat-node": "2.0.1",
     "react-bootstrap": "0.31.2",
     "react-dom": "15.6.0",