:construction_worker: ignore gh-pages branch in CircleCI

.circleci/config.yml

diff --git a/.circleci/config.yml b/.circleci/config.yml
index 0d7a847..82e5098 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -45,10 +45,12 @@
   build_and_test_all:
     jobs:
       - build_stable:
-          branches:
-            ignore:
-              gh-pages
+          filters:
+            branches:
+              ignore:
+                gh-pages
       - build_bleeding_edge:
-          branches:
-            ignore:
-              gh-pages
+          filters:
+            branches:
+              ignore:
+                gh-pages