Update travis to append nightly in develop-v4 version

Author: mrrobot47

ci/prepare.sh

@@ -2,4 +2,11 @@
 
 # called by Travis CI
 
+if [[ "$TRAVIS_BRANCH" == "develop-v4" ]]; then
+    version=$(head -n 1 VERSION)
+    version="$(echo $version | xargs)"
+    version+="-nightly"
+    echo $version > VERSION
+fi
+
 php -dphar.readonly=0 ./utils/make-phar.php easyengine.phar --quite  > /dev/null