Fix missing escaping in travis.yml

Not gonna do stuff like that in `master` again...

Author: black-puppydog

.travis.yml

@@ -42,5 +42,5 @@ branches:
   only:
   - master
   - "/^v\\d+\\.\\d+\\.\\d+$/"
-  - "/^v\\d+\\.\\d+\\.\\d+-beta.\d+$/"
-  - "/^v\\d+\\.\\d+\\.\\d+-alpha.\d+$/"
+  - "/^v\\d+\\.\\d+\\.\\d+-beta\\.\\d+$/"
+  - "/^v\\d+\\.\\d+\\.\\d+-alpha\\.\\d+$/"