upgrade Gradle wrapper

build.gradle

@@ -73,7 +73,7 @@ subprojects {
 }
 
 task wrapper(type: Wrapper) {
-    gradleVersion = '3.4.1'
+    gradleVersion = '4.0'
 }
 
 //Task used by Heroku for staging

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
-#Fri Mar 17 10:32:10 CET 2017
+#Fri Jun 23 10:27:01 CEST 2017
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-3.4.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.0-bin.zip

gradlew

@@ -33,11 +33,11 @@ DEFAULT_JVM_OPTS=""
 # Use the maximum available, or set MAX_FD != -1 to use that value.
 MAX_FD="maximum"
 
-warn ( ) {
+warn () {
     echo "$*"
 }
 
-die ( ) {
+die () {
     echo
     echo "$*"
     echo
@@ -155,7 +155,7 @@ if $cygwin ; then
 fi
 
 # Escape application args
-save ( ) {
+save () {
     for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
     echo " "
 }