Check DNS changes 4x/day; expose job output to public

- I like public output because it reassures users
  that we're really, truly testing

ci/pipeline-sslip.io.yml

@@ -6,11 +6,12 @@ groups:
   jobs:
   - check-dns
 
-
 jobs:
 - name: check-dns
+  public: true
   plan:
   - {get: sslip.io,   trigger: true}
+  - {get: 6h,         trigger: true}
   - task: check-dns
     file: sslip.io/ci/tasks/check-dns.yml
     params:
@@ -22,3 +23,7 @@ resources:
   source:
     uri: https://github.com/cunnie/sslip.io
     branch: master
+
+- name: 6h
+  type: time
+  source: {interval: 6h}