Whitelist branches for travis to build

.travis.yml

@@ -4,6 +4,16 @@ language: c
 
 sudo: false
 
+# Remember to add release branches
+# we whitelist branches, as we don't really need to build dev-branches.
+branches:
+  only:
+    - master
+    - "1.24"
+    - "1.22"
+    - "1.20"
+    - "1.18"
+
 # The following enables several GHC versions to be tested; often it's enough to
 # test only against the last release in a major GHC version. Feel free to omit
 # lines listings versions you don't need/want testing for.