Fix deprecation warning "The DefaultSourceDirectorySet constructor has been deprecated"

.travis.yml

@@ -1,6 +1,6 @@
 language: groovy
 jdk:
-  - oraclejdk8
+  - openjdk8
 install: ./gradlew resolveAllDependencies test
 before_script:
   - "echo $JAVA_OPTS"

build.gradle

@@ -1,6 +1,6 @@
 plugins {
-    id "com.gradle.plugin-publish" version "0.9.4"
-    id "com.jfrog.bintray" version "1.6"
+    id "com.gradle.plugin-publish" version "0.10.1"
+    id "com.jfrog.bintray" version "1.8.4"
 }
 
 apply plugin: 'groovy'
@@ -10,8 +10,8 @@ apply plugin: 'signing'
 apply plugin: 'idea'
 apply plugin: 'jacoco'
 
-sourceCompatibility = 1.6
-targetCompatibility = 1.6
+sourceCompatibility = 1.7
+targetCompatibility = 1.7
 
 defaultTasks 'clean', 'build'
 
@@ -225,6 +225,14 @@ def getPomConfiguration() {
 // download dependencies all at once, keeps downloads out of travis output
 task resolveAllDependencies {
     doLast {
-        configurations.all { it.resolve() }
+        configurations.all { configuration ->
+            if (configuration.isCanBeResolved()) {
+                println "Resolving $configuration"
+                configuration.resolve()
+            }
+            else {
+                println "$configuration is not resolvable"
+            }
+        }
     }
-}
+}

src/main/groovy/com/eriwen/gradle/css/source/internal/DefaultCssSourceSet.groovy

@@ -24,7 +24,9 @@ class DefaultCssSourceSet implements CssSourceSet {
     DefaultCssSourceSet(String name, Project project, Instantiator instantiator, FileResolver fileResolver) {
         this.name = name
         this.displayName = GUtil.toWords(name)
-        if (GradleVersion.current().compareTo(GradleVersion.version("2.12")) >= 0) {
+        if (GradleVersion.current().compareTo(GradleVersion.version("5.0")) >= 0) {
+            this.css = project.objects.sourceDirectorySet(name, String.format("%s CSS source", displayName))
+        } else if (GradleVersion.current().compareTo(GradleVersion.version("2.12")) >= 0) {
             Class fileTreeFactory = Class.forName("org.gradle.api.internal.file.collections.DefaultDirectoryFileTreeFactory")
             def directoryFileTreeFactory = fileTreeFactory.getConstructor().newInstance()
             this.css = new DefaultSourceDirectorySet(name, String.format("%s CSS source", displayName), fileResolver, directoryFileTreeFactory)