update site to beta 6 (#156)

Author: tinayuangao

package.json

@@ -22,7 +22,7 @@
     "@angular/core": "^4.0.0",
     "@angular/forms": "^4.0.0",
     "@angular/http": "^4.0.0",
-    "@angular/material": "^2.0.0-beta.5",
+    "@angular/material": "^2.0.0-beta.6",
     "@angular/platform-browser": "^4.0.0",
     "@angular/platform-browser-dynamic": "^4.0.0",
     "@angular/router": "~4.0.0",