Merge pull request #689 from exercism/gradle-update

Update to Gradle 4.0.1

gradle/wrapper/gradle-wrapper.properties

-#Wed Jun 14 14:21:29 EDT 2017
+#Fri Jul 07 18:07:45 EDT 2017
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.0-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.0.1-bin.zip