Updated Travis config to allow PR builds to feature branches.

The previous restriction allowed builds only when the target
branch = master or a tag with specific name pushed.

Now every tag would be allowed too.

.travis.yml

@@ -10,12 +10,8 @@ cache:
   directories:
     - '$HOME/.sonar/cache'
 
-# Build only commits on master and release tags preventing double builds for PRs
-# See https://docs.travis-ci.com/user/pull-requests/#double-builds-on-pull-requests
-branches:
-  only:
-    - master
-    - /v[0-9]+\.[0-9]+\.[0-9]+(-.*)?$/
+# Trigger build only when one of the following conditions is met
+if: type = pull_request OR branch = master OR tag IS present
 
 addons:
   sonarcloud: