Bind press keyboard event on search input box (#183)

Bind enter press event on search input box
diff --git a/dubbo-admin-frontend/src/components/ServiceSearch.vue b/dubbo-admin-frontend/src/components/ServiceSearch.vue
index f3c61c0..02f2928 100644
--- a/dubbo-admin-frontend/src/components/ServiceSearch.vue
+++ b/dubbo-admin-frontend/src/components/ServiceSearch.vue
@@ -35,6 +35,7 @@
                   :suffix="queryBy"
                   :hint="hint"
                   label="Search Dubbo Services"
+                  @keyup.enter="submit"
                 ></v-combobox>
                   <v-menu class="hidden-xs-only">
                     <v-btn slot="activator" large icon>