Publish all branches skip only pull requests

With the improved version handling in the build it is now possible to
publish multiple versions in parallel. So, we can savely publish from
branches.

Author: cboehme

travis/publish.sh

@@ -1,8 +1,8 @@
 #!/usr/bin/env bash
 
-function require_on_master {
-    if [ ! -v TRAVIS_BRANCH -o "$TRAVIS_BRANCH" != "master" ]; then
-        echo "Not on master branch. Will not publish."
+function require_no_pull_request {
+    if [ -v TRAVIS_PULL_REQUEST -a "$TRAVIS_PULL_REQUEST" != "false" ]; then
+        echo "Building pull request. Will not publish."
         exit 0
     fi
 }
@@ -78,7 +78,7 @@ function clean_gradle_configuration {
     echo "OK"
 }
 
-require_on_master
+require_no_pull_request
 require_secure_vars
 require_vars