Skip CI for default GitHub patch/revert branches.

The default naming convention for patch branches created in
the GitHub UI when editing files is: {username}-patch-{number}

The default naming convention for revert branches created in
the GitHub UI when reverting a PR is: revert-{pr_number}-{pr_branch_name}

This exclusion will prevent Shippable from running on these
branches until a PR is created.

shippable.yml

@@ -58,6 +58,12 @@ matrix:
 
     - env: TEST=cloud/ubuntu1604
     - env: TEST=cloud/ubuntu1604py3
+
+branches:
+  except:
+    - "*-patch-*"
+    - "revert-*-*"
+
 build:
   pre_ci:
     - docker images drydock/u16pytall