Update the CI images

Author: bbatsov

.circleci/config.yml

@@ -11,19 +11,19 @@ default: &default-steps
 jobs:
   test-emacs-25:
     docker:
-      - image: silex/emacs:25-dev
+      - image: silex/emacs:25-ci-cask
         entrypoint: bash
     <<: *default-steps
 
   test-emacs-26:
     docker:
-      - image: silex/emacs:26-dev
+      - image: silex/emacs:26-ci-cask
         entrypoint: bash
     <<: *default-steps
 
   test-emacs-master:
     docker:
-      - image: silex/emacs:master-dev
+      - image: silex/emacs:master-ci-cask
         entrypoint: bash
     <<: *default-steps