Merge pull request #119 from csmith/master

Upgrade gradle.

build.gradle

 
 task wrapper(type: Wrapper) {
     description 'Downloads and installs an up-to-date wrapper for gradle.'
-    gradleVersion = '3.1'
+    gradleVersion = '4.6'
 }
 

gradle/resolve-dependencies.gradle

     doLast {
         allprojects.each { subProject ->
             subProject.buildscript.configurations.each { configuration ->
-                configuration.resolve()
+                if (configuration.isCanBeResolved()) {
+	                configuration.resolve()
+		}
             }
             subProject.configurations.each { configuration ->
-                configuration.resolve()
+		if (configuration.isCanBeResolved()) {
+	                configuration.resolve()
+		}
             }
         }
     }

gradle/wrapper/gradle-wrapper.properties

-#Thu Oct 27 18:01:10 BST 2016
+#Sat Mar 31 12:30:32 BST 2018
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-3.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.6-bin.zip