Run Travis for all branches except depfu

Otherwise when working on a fork Travis doesn't run for the branch you
are working on. Now you can try things out and ensure it works before
sending a PR.

depfu branches keep excluded as it will cause that we run it twice.

.travis.yml

@@ -5,8 +5,8 @@ cache: bundler
 rvm:
   - 2.5.0@osem --ignore-gemsets
 branches:
-  only:
-    - master
+  except:
+    - /^depfu/.*$/
 before_install:
   - "echo 'gem: --no-ri --no-rdoc' > ~/.gemrc"
   - "echo `phantomjs -v`"