Add junit5 to build infra

- Fixes #772

build.gradle

@@ -111,6 +111,7 @@ configure(allprojects) {
 	}
 
 	test {
+		useJUnitPlatform()
 		exclude '**/*IntegrationTests.*'
 	}
 }
@@ -118,6 +119,12 @@ configure(allprojects) {
 configure(subprojects) { subproject ->
 	apply from: "${rootProject.projectDir}/publish-maven.gradle"
 
+	dependencies {
+		testCompile("org.junit.jupiter:junit-jupiter-api")
+		testRuntime("org.junit.jupiter:junit-jupiter-engine")
+		testRuntime("org.junit.vintage:junit-vintage-engine")
+	}
+
 	jar {
 		manifest.attributes['Implementation-Title'] = subproject.name
 		manifest.attributes['Implementation-Version'] = subproject.version