Update gradle to 3.1.

build.gradle

 apply from: 'gradle/fatjar.gradle'
 
 task wrapper(type: Wrapper) {
-    gradleVersion = '2.13'
+    gradleVersion = '3.1'
 }

gradle/wrapper/gradle-wrapper.properties

-#Thu May 05 16:29:58 BST 2016
+#Thu Oct 27 18:04:08 BST 2016
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-2.13-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-3.1-bin.zip

gradlew

 ##
 ##############################################################################
 
-# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
-DEFAULT_JVM_OPTS=""
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
 
 APP_NAME="Gradle"
 APP_BASE_NAME=`basename "$0"`
 
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS=""
+
 # Use the maximum available, or set MAX_FD != -1 to use that value.
 MAX_FD="maximum"
 
 cygwin=false
 msys=false
 darwin=false
+nonstop=false
 case "`uname`" in
   CYGWIN* )
     cygwin=true
   MINGW* )
     msys=true
     ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
 esac
 
-# Attempt to set APP_HOME
-# Resolve links: $0 may be a link
-PRG="$0"
-# Need this for relative symlinks.
-while [ -h "$PRG" ] ; do
-    ls=`ls -ld "$PRG"`
-    link=`expr "$ls" : '.*-> \(.*\)$'`
-    if expr "$link" : '/.*' > /dev/null; then
-        PRG="$link"
-    else
-        PRG=`dirname "$PRG"`"/$link"
-    fi
-done
-SAVED="`pwd`"
-cd "`dirname \"$PRG\"`/" >/dev/null
-APP_HOME="`pwd -P`"
-cd "$SAVED" >/dev/null
-
 CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
 
 # Determine the Java command to use to start the JVM.
 fi
 
 # Increase the maximum file descriptors if we can.
-if [ "$cygwin" = "false" -a "$darwin" = "false" ] ; then
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
     MAX_FD_LIMIT=`ulimit -H -n`
     if [ $? -eq 0 ] ; then
         if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
 eval splitJvmOpts $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS
 JVM_OPTS[${#JVM_OPTS[*]}]="-Dorg.gradle.appname=$APP_BASE_NAME"
 
+# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
+if [[ "$(uname)" == "Darwin" ]] && [[ "$HOME" == "$PWD" ]]; then
+  cd "$(dirname "$0")"
+fi
+
 exec "$JAVACMD" "${JVM_OPTS[@]}" -classpath "$CLASSPATH" org.gradle.wrapper.GradleWrapperMain "$@"

gradlew.bat

 @rem Set local scope for the variables with windows NT shell
 if "%OS%"=="Windows_NT" setlocal
 
-@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
-set DEFAULT_JVM_OPTS=
-
 set DIRNAME=%~dp0
 if "%DIRNAME%" == "" set DIRNAME=.
 set APP_BASE_NAME=%~n0
 set APP_HOME=%DIRNAME%
 
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS=
+
 @rem Find java.exe
 if defined JAVA_HOME goto findJavaFromJavaHome
 
 @rem Get command-line arguments, handling Windows variants
 
 if not "%OS%" == "Windows_NT" goto win9xME_args
-if "%@eval[2+2]" == "4" goto 4NT_args
 
 :win9xME_args
 @rem Slurp the command line arguments.
 if "x%~1" == "x" goto execute
 
 set CMD_LINE_ARGS=%*
-goto execute
-
-:4NT_args
-@rem Get arguments from the 4NT Shell from JP Software
-set CMD_LINE_ARGS=%$
 
 :execute
 @rem Setup the command line