Force source compatibility to JDK8 and bump our minor version

Author: R. Tyler Croy

build.gradle

@@ -15,8 +15,10 @@ buildscript {
 apply plugin: 'idea'
 
 group = 'com.github.jruby-gradle'
-version = '1.4.0'
+version = '1.5.0'
 defaultTasks 'check', 'assemble'
+sourceCompatibility = '1.8'
+targetCompatibility = '1.8'
 
 if (!releaseBuild) {
     version = "${version}-SNAPSHOT"
@@ -62,8 +64,8 @@ subprojects {
     }
 
     plugins.withType(JavaPlugin) {
-        sourceCompatibility = 1.7
-        targetCompatibility = 1.7
+        sourceCompatibility = 1.8
+        targetCompatibility = 1.8
 
 
         project.tasks.withType(JavaCompile) { task ->