revamp saved search implementation

db/migrate/20170314235626_add_tags_to_saved_searches.rb

@@ -0,0 +1,7 @@
+class AddTagsToSavedSearches < ActiveRecord::Migration
+  def change
+  	add_column :saved_searches, :labels, "text", array: true, null: false, default: []
+  	add_index :saved_searches, :labels, using: :gin
+  	rename_column :saved_searches, :tag_query, :query
+  end
+end